Author name code: vargas-dominguez
ADS astronomy entries on 2022-09-14
author:"Vargas Dominguez, Santiago"
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Title: Energy transport during 3D small-scale reconnection driven
by anisotropic plasma turbulence
Authors: Agudelo Rueda, Jeffersson A.; Verscharen, Daniel; Wicks,
Robert T.; Owen, Christopher J.; Nicolaou, Georgios; Germaschewski,
Kai; Walsh, Andrew P.; Zouganelis, Ioannis; Vargas Domínguez, Santiago
Bibcode: 2022arXiv220802350A
Altcode:
Energy dissipation in collisionless plasmas is a longstanding
fundamental physics problem. Although it is well known that magnetic
reconnection and turbulence are coupled and transport energy
from system-size scales to sub-proton scales, the details of the
energy distribution and energy dissipation channels remain poorly
understood. Especially, the energy transfer and transport associated
with three dimensional (3D) small-scale reconnection that occurs as
a consequence of a turbulent cascade is unknown. We use an explicit
fully kinetic particle-in-cell code to simulate 3D small scale
magnetic reconnection events forming in anisotropic and Alfvénic
decaying turbulence. We identify a highly dynamic and asymmetric
reconnection event that involves two reconnecting flux ropes. We use
a two-fluid approach based on the Boltzmann equation to study the
spatial energy transfer associated with the reconnection event and
compare the power density terms in the two-fluid energy equations with
standard energy-based damping, heating and dissipation proxies. Our
findings suggest that the electron bulk flow transports thermal energy
density more efficiently than kinetic energy density. Moreover, in our
turbulent reconnection event, the energy-density transfer is dominated
by plasma compression. This is consistent with turbulent current sheets
and turbulent reconnection events, but not with laminar reconnection.
Title: The pioneering scientific endeavor of the first Colombian
modern astronomer José María González Benito (1843-1903)
Authors: Moreno Cárdenas, Freddy; Vargas Domínguez, Santiago;
Cuellar, Jorge
Bibcode: 2022arXiv220408097M
Altcode:
Astronomical interest within the current Colombian territory has
its roots in the Botanical Expedition of the New Kingdom of Granada,
which stimulated the creation of an astronomical observatory in 1803,
the first one established in the New World to pursue systematic
observations and meteorological studies. After the death in 1816 of
its first director, Francisco José de Caldas, during the convulsive
independence period, no major astronomical observations were made
for decades, with few exceptions. In this work we delve into the
contributions of the astronomer José María González Benito, the main
reactivator of the National Astronomical Observatory of Colombia in the
second half of the 19th century, pointing out his pioneering efforts
that put worldwide attention to it, and to his own private observatory
making him one of the most committed figures to the development of
astronomical sciences in the country and the most renowned Colombian
in the international astronomical research scene of his time.
Title: Observational evidence for two-component distributions
describing solar magnetic bright points
Authors: Berrios Saavedra, Gerardine; Utz, Dominik; Vargas Domínguez,
Santiago; Campos Rozo, José Iván; González Manrique, Sergio Javier;
Gömöry, Peter; Kuckein, Christoph; Balthasar, Horst; Zelina, Peter
Bibcode: 2022A&A...657A..79B
Altcode: 2021arXiv211012404B
Context. High-resolution observations of the solar photosphere reveal
the presence of fine structures, in particular the so-called Magnetic
Bright Points (MBPs), which are small-scale features associated with
strong magnetic field regions of the order of kilogauss (kG). It
is especially relevant to study these magnetic elements, which are
extensively detected in all moments during the solar cycle, in order to
establish their contribution to the behavior of the solar atmosphere,
and ultimately a plausible role within the coronal heating problem.
Aims: Characterisation of size and velocity distributions of MBPs in
the solar photosphere in two different datasets of quiet Sun images
acquired with high-resolution solar instruments i.e. Solar Optical
Telescope SOT/Hinode and the High-resolution Fast Imager HiFI/GREGOR,
in the G-band (4308 Å).
Methods: In order to detect the
MBPs, an automatic segmentation and identification algorithm is
used. Next, the identified features were tracked to measure their
proper motions. Finally, a statistical analysis of hundreds of MBPs is
carried out, generating histograms for areas, diameters and horizontal
velocities.
Results: This work establishes that areas and
diameters of MBPs display log-normal distributions that are well-fitted
by two different components, whereas the velocity vector components
follow Gaussians and the vector magnitude a Rayleigh distribution
revealing again for all vector elements a two component composition.
Conclusions: The results can be interpreted as due to the presence of
two different populations of MBPs in the solar photosphere one likely
related to stronger network magnetic flux elements and the other one
to weaker intranetwork flux elemens. In particular this work concludes
on the effect of the different spatial resolution of GREGOR and Hinode
telescopes, affecting detections and average values.
Title: 3D Small-scale Turbulent Reconnection: Energy Transport
and Transfer.
Authors: Agudelo Rueda, Jeffersson Andres; Verscharen, Daniel;
Wicks, Robert; Owen, Christopher; Germaschewski, Kai; Walsh, Andrew;
Zouganelis, Yannis; Nicolaou, Georgios; Vargas-Dominguez, Santiago
Bibcode: 2021AGUFMSH54B..07A
Altcode:
Energy dissipation in collisionless plasmas is a longstanding
problem. Although it is well known that magnetic reconnection and
turbulence transport energy from system-size scales to subptroton
scales, the details of the energy distribution and energy dissipation
channels remain poorly understood. Moreover, the energy distribution
associated with 3D small reconnection that occurs from a turbulent
cascade is not entirely clear. To get some insight on this matter,
we use an explicit fully kinetic particle-in-cell code to simulate 3D
small scale magnetic reconnection events forming in anisotropic and
Alfvénic decaying turbulence. We define a set of indicators to find
reconnection sites in our simulation based on intensity thresholds. With
these indicators, we identify the occurrence of reconnection events in
the simulation domain and analyse one of these events in detail. The
event involves two reconnecting flux ropes. It is highly dynamic and
asymmetric. We use a two-fluid approach to study the spatial energy
distribution associated with the reconnection event and compare the
power density terms in the two-fluid energy equations with standard
energy-based dissipation surrogates. Our findings suggest that the
distribution of the thermal energy is controlled by the region between
the reconnecting flux ropes whereas the kinetic energy is associated
with the inner part of the flux ropes.
Title: Evidence For Two-component Distributions Describing Magnetic
Bright Points In The Solar Photosphere
Authors: Vargas Domínguez, S.; Berrios Saavedra, G.; Utz, D.;
Campos Rozo, J. I.; González Manrique, S.; Gömöry, Peter; Kuckein,
Christoph; Balthasar, Horst; Zelina, Peter
Bibcode: 2021AAS...23811310V
Altcode:
High-resolution observations of the Sun reveal the presence of Magnetic
Bright Points (MBPs), which are small-scale features associated with
strong magnetic field regions, that are found all over the solar
photosphere. In this work, we characterize some physical properties
and dynamics of MBPs in a quiet Sun region by using time series of
images acquired with the High-resolution Fast Imager HiFI/GREGOR and
Solar Optical Telescope SOT/Hinode in the G-band (4308 Angstrom). An
automated segmentation algorithm is used to identify the MBPs and
track their evolution. The results show observational evidence for
two-component distributions of areas, diameters and velocities, that
can be interpreted as corresponding to different populations of MBPs.
Title: The active region source of a type III radio storm observed
by Parker Solar Probe during encounter 2
Authors: Harra, L.; Brooks, D. H.; Bale, S. D.; Mandrini, C. H.;
Barczynski, K.; Sharma, R.; Badman, S. T.; Vargas Domínguez, S.;
Pulupa, M.
Bibcode: 2021A&A...650A...7H
Altcode: 2021arXiv210204964H
Context. We investigated the source of a type III radio burst storm
during encounter 2 of NASA's Parker Solar Probe (PSP) mission.
Aims: It was observed that in encounter 2 of NASA's PSP mission there
was a large amount of radio activity and, in particular, a noise storm
of frequent, small type III bursts from 31 March to 6 April 2019. Our
aim is to investigate the source of these small and frequent bursts.
Methods: In order to do this, we analysed data from the Hinode EUV
Imaging Spectrometer, PSP FIELDS, and the Solar Dynamics Observatory
Atmospheric Imaging Assembly. We studied the behaviour of active region
12737, whose emergence and evolution coincides with the timing of the
radio noise storm and determined the possible origins of the electron
beams within the active region. To do this, we probed the dynamics,
Doppler velocity, non-thermal velocity, FIP bias, and densities,
and carried out magnetic modelling.
Results: We demonstrate
that although the active region on the disc produces no significant
flares, its evolution indicates it is a source of the electron beams
causing the radio storm. They most likely originate from the area
at the edge of the active region that shows strong blue-shifted
plasma. We demonstrate that as the active region grows and expands,
the area of the blue-shifted region at the edge increases, which is
also consistent with the increasing area where large-scale or expanding
magnetic field lines from our modelling are anchored. This expansion
is most significant between 1 and 4 April 2019, coinciding with the
onset of the type III storm and the decrease of the individual burst's
peak frequency, indicating that the height at which the peak radiation
is emitted increases as the active region evolves.
Title: Three-dimensional magnetic reconnection in particle-in-cell
simulations of anisotropic plasma turbulence
Authors: Agudelo Rueda, Jeffersson A.; Verscharen, Daniel; Wicks,
Robert T.; Owen, Christopher J.; Nicolaou, Georgios; Walsh, Andrew P.;
Zouganelis, Ioannis; Germaschewski, Kai; Vargas Domínguez, Santiago
Bibcode: 2021JPlPh..87c9028A
Altcode: 2021arXiv210313232A
We use three-dimensional (3-D) fully kinetic particle-in-cell
simulations to study the occurrence of magnetic reconnection
in a simulation of decaying turbulence created by anisotropic
counter-propagating low-frequency Alfvén waves consistent with
critical-balance theory. We observe the formation of small-scale
current-density structures such as current filaments and current
sheets as well as the formation of magnetic flux ropes as part of
the turbulent cascade. The large magnetic structures present in the
simulation domain retain the initial anisotropy while the small-scale
structures produced by the turbulent cascade are less anisotropic. To
quantify the occurrence of reconnection in our simulation domain,
we develop a new set of indicators based on intensity thresholds to
identify reconnection events in which both ions and electrons are
heated and accelerated in 3-D particle-in-cell simulations. According
to the application of these indicators, we identify the occurrence
of reconnection events in the simulation domain and analyse one of
these events in detail. The event is related to the reconnection
of two flux ropes, and the associated ion and electron exhausts
exhibit a complex 3-D structure. We study the profiles of plasma
and magnetic-field fluctuations recorded along artificial-spacecraft
trajectories passing near and through the reconnection region. Our
results suggest the presence of particle heating and acceleration
related to small-scale reconnection events within magnetic flux ropes
produced by the anisotropic Alfvénic turbulent cascade in the solar
wind. These events are related to current structures of the order of
a few ion inertial lengths in size.
Title: Comparative Analysis of Sky Quality and Meteorological
Variables During the Total Lunar Eclipse on 14-15 April 2014 and
their Effect on Qualitative Measurements of the Bortle Scale
Authors: Góez Therán, C.; Vargas Domínguez, S.
Bibcode: 2021RMxAA..57...57G
Altcode: 2020arXiv200908225G
A total lunar eclipse plausibly has an influence on the variation of
some environmental physical parameters, specifically on the conditions
of the sky brightness, humidity and temperature. During the eclipse
on 14th -15th April 2014, these parameters
were measured with a photometer and a weather station. The obtained
results allow the comparison, practically, of the optimal conditions
for observational astronomy work in the Tatacoa desert and, therefore,
to certify it as suitable place to develop night sky astronomical
observations. This investigation determined, to some extent, the
suitability of this place to carry out astronomical work and research
within the optical range. Thus, the changes recorded during the
astronomical phenomenon allowed the classification of the sky based
on the Bortle Scale.
Title: Spontaneous Reconnection in Three-Dimensional Particle-In-Cell
Simulations of Collisionless Plasma Turbulence
Authors: Agudelo Rueda, J. A.; Verscharen, D.; Wicks, R. T.; Owen,
C. J.; Nicolaou, G.; Walsh, A. P.; Zouganelis, Y.; Germaschewski,
K.; Vargas-Dominguez, S.
Bibcode: 2020AGUFMSH055..02A
Altcode:
We use 3D fully kinetic particle-in-cell simulations to study the
spontaneous formation of magnetic reconnection as a self-consistent
component of the turbulent cascade under solar-wind-like conditions. We
simulate anisotropic decaying Alfvénic turbulence created by the
collision of counter-propagating low-frequency Alfvén waves. The
initial wavevector anisotropy is consistent with critical-balance
theory. We observe the creation of small-scale current density
structures such as current filaments and current sheets as well as the
formation of magnetic flux ropes as part of the turbulent cascade. We
develop a new set of indicators to find reconnection regions in 3D
Particle-in-cell simulations. According to the application of these
indicators, we observe the spontaneous creation of reconnection events
in the simulation domain. We analyse one of the reconnection events
associated with a twisted flux rope in detail. This event is highly
dynamic and asymmetric. We study the profiles of plasma bulk quantities
recorded by artificial-spacecraft trajectories passing near and through
the reconnection region. Our results suggest that the particle heating
and acceleration related to asymmetric small-scale reconnection events
are located within magnetic flux tubes produced by the anisotropic
Alfvénic turbulent cascade in the solar wind.
Title: Analysis of magnetic polarities in active regions for the
prediction of solar flares
Authors: Granados, Natalia; Vargas Domínguez, Santiago
Bibcode: 2020RACCE..44..984G
Altcode:
Solar active regions, and the processes that occur in them, have been
extensively studied and analyzed, generating many types of models and
characterizations for the occurrence of different eruptive events that
take place in the solar atmosphere. Within these regions, the most
characteristic ones are those that have opposite magnetic polarity
and that, in their majority, generate explosive events, such as the
so-called solar flares. The flares are intense explosions occurring
in the solar atmosphere which can have adverse effects on the Earth
and the technology developed by humans, as well as being determining
factors in the so-called space weather. For this reason, attempts have
been made to predict the occurrence of these events. In this work,
a predictive model of solar flares higher than M5 will be developed
based on the articles proposed by Korsos et.al., (2014, 2015), using
the relationship between the flares and the active bipolar regions. The
analysis takes into account the areas of the sunspots' umbra of opposite
polarity, their average magnetic field and the magnetic barycenter's
of each sunspot in the region for a sample of three active regions,
finding their temporal variation due to the evolution of the sunspots,
confirming previous work in the literature. A statistical analysis
is carried out to inspect whether after the occurrence of a flare,
another can arise in subsequent hours.
Title: Analysis of magnetic polarities in active regions for the
prediction of solar flares
Authors: Granados Hernández, N.; Vargas Domínguez, S.
Bibcode: 2020arXiv201204050G
Altcode:
Solar active regions and the processes that occur in them have
been extensively studied and analyzed and many types of models and
characterizations have been proposed for the occurrence of different
eruptive events that take place in the solar atmosphere. The most
characteristic of these regions are those that have opposite magnetic
polarity, which, in their majority, generate explosive events such as
the so-called solar flares. The flares are intense explosions occurring
in the solar atmosphere with adverse effects on the Earth and the
technology developed by humans, and they are also determining factors
in the so-called space weather. For this reason, attempts have been
made to predict the occurrence of these events. In the present study,
we developed a predictive model of solar flares higher than M5 based
on the articles proposed by Korsos, et al. (2014, 2015) using the
relationship between the flares and the bipolar active regions. The
analysis took into account the areas of the umbrae of opposite
polarity, their average magnetic field, and the magnetic barycenter
from each sunspot in the region for a sample of three active regions
to find the temporal variation due to the evolution of the sunspots,
thus confirming previous results reported in the literature. We made
a statistical analysis to determine whether after a flare occurs,
another can arise in the subsequent hours.
Title: Dynamics and Flows in Active Region NOAA12737 that can
contribute to Type III Bursts observed by Parker Solar Probe during
Encounter 2.
Authors: Harra, L.; Brooks, D.; Barczynski, K.; Mandrini, C. H.;
Vargas-Dominguez, S.; Bale, S.; Badman, S. T.; Raouafi, N. E.;
Rouillard, A. P.
Bibcode: 2020AGUFMSH0240001H
Altcode:
We have analysed solar activity on the Sun during encounter 2 of the
Parker Solar Probe mission. We studied the period from 30th
March to 4th April when a small active region (NOAA 12737)
emerged. This active region showed no significant flaring. During this
time period there were however, an increasing number of type III bursts
measured by the FIELDS instrument. We analyse solar data from SDO-AIA,
SDO-HMI and Hinode EIS to determine what the potential sources of
the type III bursts could be, which occur on timescales of tens of
seconds. The active region core shows small brightenings in EUV and
X-ray wavebands, but these are not continuous, and seem unlikely to be
connected. There are magnetic field changes due to the active region
emergence, which occur on timescales of hours rather than seconds. There
are small scale magnetic flux emergences but these are not frequent
enough to be linked to the continuous type III bursts. As the active
region emerges, we track the upflows at the edge of the active region
as they are created and evolve. We show evidence of variations in the
upflows that seem to be the most likely candidates for the sources of
the type III bursts.
Title: Automatic Detection of Light Bridges in Solar Active Regions
Based on Deep Learning Techniques
Authors: Alfonso Soler, Bryan; Vargas Domínguez, Santiago; Martínez
Galarza, Juan Rafael
Bibcode: 2020SPD....5120201A
Altcode:
Understanding the nature of the phenomena that occur in the solar
surface (photosphere) is greatly benefited from the technical
capabilities of the new instruments, located either in terrestrial
or space telescopes, providing ever greater spatial and temporal
resolution, and therefore, allowing detailed observations of
photospheric structures. In particular, new observations have revealed
the intricate configuration of sunspots and substructures within
them, such as so-called light bridges. Eventually, depending on its
morphology and structure, light bridges can alter the evolution of
the host sunspot, both in morphology and in other of its physical
properties, playing a role on other phenomena such as magnetic
reconnection or coronal rain, associated with energy releases in
the solar atmosphere. This work presents the development of an
identification method of light bridges in sunspots, through the initial
implementation of an algorithm for the automatic detection, extraction
and characterization of these structures, followed by the application
of supervised classification techniques based on Machine Learning (ML)
Convolutional Neural Networks (CNN). By using a sample of 265 active
regions, over a period of 4 years from 2010 to 2014, with a cadence
of 24 hours for each sunspot, from full-disk observations acquired
by the Solar Dynamics Observatory (SDO) with the Helioseysmic and
Magnetic Imager (HMI) instrument in the FeI (617 Å) line. Detection
accuracy of 85.4% is reached, optimizing the model by the iterative
variation of the hyperparameters according to the binary classification
addressed. The method is planned to be further implemented to probe
the dynamics of light bridges and their connection with the evolution
of the corresponding active region.
Title: FM14 Session 2: Communicating Astronomy in our Changing World
Authors: Waller, William H.; Canas, Lina; Agata, Hidehiko; Yamaoka,
Hitoshi; Karino, Shigeyuki; Cenadelli, Davide; Ettore Bernagozzi,
Andrea; Christille, Jean Marc; Benedetto, Matteo; Calabrese, Matteo;
Calcidese, Paolo; Gelderman, Richard; Hayashi, Saeko S.; Lubowich,
Donald; Madura, Thomas; Christian, Carol; Hurd, David; Silberman, Ken;
Walker, Kyle; McVoy, Shannon; Massey, Robert; Radajewski, Bogumił;
Mikołajewski, Maciej; Czart, Krzysztof; Guz, Iwona; Rubaszewski,
Adam; Stelmach, Tomasz; Ros, Rosa M.; Viñuales, Ederlinda; Garca,
Beatriz; Sánchez, Yuly E.; Vargas Domínguez, Santiago; Acosta,
Cesar; Rodríguez, Nayive; Sekhar, Aswin; Sundin, Maria; Andersson,
Petra; Finnsgård, Christian; Larsson, Lars; Miller, Ron; Tomita,
Akihiko; Wadadekar, Yogesh
Bibcode: 2020IAUGA..30..528W
Altcode:
As the IAU heads towards its second century, many changes have
simultaneously transformed Astronomy and the human condition
world-wide. Amid the amazing recent discoveries of exoplanets, primeval
galaxies, and gravitational radiation, the human condition on Earth has
become blazingly interconnected, yet beset with ever-increasing problems
of over-population, pollution, and never-ending wars. Fossil-fueled
global climate change has begun to yield perilous consequences. And
the displacement of people from war-torn nations has reached levels
not seen since World War II.
Title: The Educational and Influential Power of the Sun
Authors: Cárdenas Avendaño, Alejandro; Vargas Domínguez, Santiago;
Moreno Cárdenas, Freddy; Calvo Mozo, Benjamin
Bibcode: 2019CAPJ...25...28C
Altcode:
This paper aims to encourage science educators and outreach groups to
use the Sun as a tool to teach science in formal and informal education
settings. We explain how the Sun can be used as a topic in this manner
and share our experience across the educational spectrum in Colombia
and how we have used it to drive development beyond astronomy.
Title: Photospheric plasma and magnetic field dynamics during the
formation of solar AR 11190
Authors: Campos Rozo, J. I.; Utz, D.; Vargas Domínguez, S.; Veronig,
A.; Van Doorsselaere, T.
Bibcode: 2019A&A...622A.168C
Altcode: 2019arXiv190102437C
Context. The Sun features on its surface typical flow patterns called
the granulation, mesogranulation, and supergranulation. These patterns
arise due to convective flows transporting energy from the interior
of the Sun to its surface. The other well known elements structuring
the solar photosphere are magnetic fields arranged from single,
isolated, small-scale flux tubes to large and extended regions
visible as sunspots and active regions.
Aims: In this paper
we will shed light on the interaction between the convective flows
in large-scale cells as well as the large-scale magnetic fields in
active regions, and investigate in detail the statistical distribution
of flow velocities during the evolution and formation of National
Oceanic and Atmospheric Administration active region 11190.
Methods: To do so, we employed local correlation tracking methods
on data obtained by the Solar Dynamics Observatory in the continuum
as well as on processed line-of-sight magnetograms.
Results:
We find that the flow fields in an active region can be modelled by a
two-component distribution. One component is very stable, follows a
Rayleigh distribution, and can be assigned to the background flows,
whilst the other component is variable in strength and velocity
range and can be attributed to the flux emergence visible both in
the continuum maps as well as magnetograms. Generally, the plasma
flows, as seen by the distribution of the magnitude of the velocity,
follow a Rayleigh distribution even through the time of formation
of active regions. However, at certain moments of large-scale fast
flux emergence, a second component featuring higher velocities is
formed in the velocity magnitudes distribution.
Conclusions:
The plasma flows are generally highly correlated to the motion of
magnetic elements and vice versa except during the times of fast
magnetic flux emergence as observed by rising magnetic elements. At
these times, the magnetic fields are found to move faster than the
corresponding plasma. Movie attached to Fig. 1 is available at https://www.aanda.org
Title: Modelling the solar photospheric plasma and magnetic field
dynamics during the emergence of AR 11190
Authors: Campos Rozo, Jose Ivan; Utz, Dominik; Veronig, Astrig;
Vargas Domínguez, Santiago
Bibcode: 2018nspm.confE...1C
Altcode:
The interaction between the plasma and the magnetic field has been
studied before by various authors. In this work we will show a
detailed study employing two different distributions applied to the
flow velocities during the emergence and prior evolution of AR 11190
on 11- April-2011. The velocity fields are computed from intensity as
well as LOS magnetograms by using Local Correlation Tracking (LCT)
techniques. Horizontal velocities as well as vertical velocities
show strong correlation between the emergence of new fast and strong
positive magnetic elements, and strong divergences observed from
vertical velocities calculated by LCT in continuum data. Although
there are several divergence regions within the field of view, just
the region of interest shows the emergences of new magnetic field.
Title: Analysis of large-scale photospheric dynamics during the
solar cycle 24
Authors: Quintero Ortega, Valeria; Vargas Domínguez, Santiago;
Campos Rozo, Jose Ivan
Bibcode: 2018ScTec..23..288Q
Altcode:
The analysis of the movements of the solar photosphere has been used by
several authors to study the dynamics of solar plasma at various spatial
and temporal scales. This work, in particular, is focused on the study
of vertical movements, in order to perform a statistical analysis of
the flow maps to characterize some dynamic aspects of the photospheric
plasma along the time evolution of the Sun. To carry out this analysis,
we used a set of images obtained by the HMI instrument HMI (Helioseismic
and Magnetic Imager) aboard the SDO mission (Solar Dynamics Observatory)
to which local correlation tracking algorithms (LCT) were applied. they
allow the identification of areas of convergence and divergence of
the plasma at certain time intervals during the solar cycle 24, thus
covering moments of high and low solar activity. The study gives us
the reason for the meridional movements showing that in low latitudes
the outgoing emergency flow occupied a higher percentage of area,
while in the latitudes near the poles the behavior changes, that is,
the incoming flows occupy a greater area.
Title: Modelling the solar photospheric plasma and magnetic field
dynamics in the quiet Sun and comparison of these results with the
flow fields in an evolving active region
Authors: Campos Rozo, Jose Ivan; Utz, Dominik; Veronig, Astrid;
Vargas Domínguez, Santiago
Bibcode: 2018simi.conf...37C
Altcode:
In the present work a detailed study of the flow velocities of a quiet
solar region is made and then compared with the flow fields during the
emergence and prior to the evolution of AR-11190 on 11-April-2010. The
velocity fields are computed from intensity as well as LOS magnetograms
by using Local Correlation Tracking (LCT) techniques. The magnitudes
of the obtained velocity vectors can be modelled by a single and
simple Rayleigh distribution in the case of the quiet Sun and by a
combination of two different statistical distributions in the case of
the active region. Primarily this combination consists of a Rayleigh
distribution that models the background velocity magnitudes as well
as the general behavior of the combined velocity distribution, plus
a weaker additional component that recreates the fast changes within
the field of view. We propose two different distributions (implying
different physical interpretations) for this second component of our
combined fitting model. Generally, we can say that all the distributions
show a strong correlation between the plasma motions and the movements
of magnetic elements except during time instances when strong and fast
magnetic flux elements start to appear within the region of interest.
Title: Fine Structure and Dynamics of the Solar Atmosphere
Authors: Vargas Domínguez, S.; Kosovichev, A. G.; Antolin, P.;
Harra, L.
Bibcode: 2017IAUS..327.....V
Altcode:
No abstract at ADS
Title: A Python-based interface to examine motions in time series
of solar images
Authors: Campos-Rozo, J. I.; Vargas Domínguez, S.
Bibcode: 2017IAUS..327...25C
Altcode:
Python is considered to be a mature programming language, besides of
being widely accepted as an engaging option for scientific analysis in
multiple areas, as will be presented in this work for the particular
case of solar physics research. SunPy is an open-source library based
on Python that has been recently developed to furnish software tools
to solar data analysis and visualization. In this work we present a
graphical user interface (GUI) based on Python and Qt to effectively
compute proper motions for the analysis of time series of solar
data. This user-friendly computing interface, that is intended to be
incorporated to the Sunpy library, uses a local correlation tracking
technique and some extra tools that allows the selection of different
parameters to calculate, vizualize and analyze vector velocity fields
of solar data, i.e. time series of solar filtergrams and magnetograms.
Title: Initiation and chromospheric effects of a M1.0 class solar
flare from high-resolution multi-wavelength observations
Authors: Sadykov, V. M.; Kosovichev, A. G.; Sharykin, I. N.; Zimovets,
I. V.; Vargas Dominguez, S.
Bibcode: 2017IAUS..327..103S
Altcode:
Initiation and development of a M 1.0 class flare of June 12, 2014, was
observed by space and ground-based telescopes, including EUV and X-ray
imaging spectroscopy by IRIS and RHESSI, and high-resolution optical
imaging by 1.6 m New Solar Telescope (NST). Analyzing the NST data,
we found small-scale loop-like structures in the region of the magnetic
field Polarity Inversion Line (PIL), the emergence and interaction of
which caused photospheric brightenings temporarily coinciding with hard
X-ray impulses. Detailed studies of the PIL region reveal signatures of
photospheric plasma downflows and dissipation of electric currents. The
reconstructed magnetic field topology shows a bundle of lines connecting
the PIL region with the flare ribbons which were places of chromospheric
evaporation observed by IRIS. The observations suggest a scenario with
the primary energy release processes located in the low atmospheric
layers of the PIL, energizing the overlying large-scale magnetic
structure and causing ``gentle'' chromospheric evaporation.
Title: Polar Facular Observations by the Zurich Observatory: A Window
to the Evolution of the Polar Fields during the Weakest Cycles of
the Last 200 Years
Authors: Vargas-Acosta, Juan Pablo; Munoz-Jaramillo, Andres; Vargas
Dominguez, Santiago; Svalgaard, Leif
Bibcode: 2017SPD....48.0501V
Altcode:
The solar polar magnetic fields are believed to be a surface
manifestation of the large-scale field that acts as the seed for
each solar cycle. Because of this, they have received a lot of recent
attention as the best proxy for solar cycle prediction.Polar magnetic
fields have been measured systematically since the 1970s and polar
facular counts (which are directly correlated with polar field strength)
have been used to infer the evolution of the polar fields going back to
1906. However, this period does not cover the solar minima of cycle 12
and 13 which preceded the weakest cycles of the last 200 years. These
cycles are of great interest due to their similarity with solar cycle
24, which was preceded by the deepest minimum observed so far during
the space age.Here we present the results of a project to count polar
faculae using recently digitized and released observations taken by
the Zurich Observatory (1887 to 1937). These observations have the
potential of extending our proxy for the polar fields further back
into this period of great interest and help us test the validity of
our understanding.
Title: Update on a Solar Magnetic Catalog Spanning Four Solar Cycles
Authors: Vargas-Acosta, Juan Pablo; Munoz-Jaramillo, Andres; Vargas
Dominguez, Santiago; Werginz, Zachary; DeLuca, Michael D.; Longcope,
Dana; Harvey, J. W.; Windmueller, John; Zhang, Jie; Martens, Petrus C.
Bibcode: 2017SPD....4811202V
Altcode:
Bipolar magnetic regions (BMRs) are the cornerstone of solar
cycle propagation, the building blocks that give structure to the
solar atmosphere, and the origin of the majority of space weather
events. However, in spite of their importance, there is no homogeneous
BMR catalog spanning the era of systematic solar magnetic field
measurements. Here we present the results of an ongoing project to
address this deficiency applying the Bipolar Active Region Detection
(BARD) code to magnetograms from the 512 Channel of the Kitt Peak
Vaccum Telescope, SOHO/MDI, and SDO/HMI.The BARD code automatically
identifies BMRs and tracks them as they are rotated by differential
rotation. The output of the automatic detection is supervised by a human
observer to correct possible mistakes made by the automatic algorithm
(like incorrect pairings and tracking mislabels). Extra passes are made
to integrate fragmented regions as well as to balance the flux between
BMR polarities. At the moment, our BMR database includes nearly 10,000
unique objects (detected and tracked) belonging to four separate solar
cycles (21-24).
Title: The effect of Cepheids exhibitting blending, bumps, eclipses
and period changes on the Period-Luminosity relation
Authors: Muñoz, J. R.; García-Varela, A.; Sabogal, B. E.; Vargas
Domínguez, S.; Martínez, J.
Bibcode: 2017RMxAC..49..165M
Altcode:
The study of structural breaks (non-linearity) on the Period-Luminosity
relation began more than seven decades ago. Since then, some studies
has found breaks in the Period-Luminosity relation. The objective in
this work is to look for possible statistical causes of these breaks
by means of robust techniques, instead of Ordinary Least Squares,
to fit linear regression to OGLE-II and OGLE-IV data. These robust
methods allow us to deal with influential points whose presence is a
violation to the Ordinary Least Squares assumptions. In fact, fitting
the models using M and MM-regressions, we do not find evidence to say
that Period-Luminosity relation is non-linear in the LMC. Therefore,
light curves of Cepheids suggesting blending, bumps, eclipses and period
changes do not have an effect on the Period-Luminosity relation in
this galaxy. On the contrary, for SMC, maybe, because of the geometry
of the galaxy, there is a possible effect these stars and adequate
models could not be found.
Title: The Carrington Event and observation of aurorae at very
low latitudes
Authors: Moreno Cárdenas, F.; Cristancho Sánchez, S.; Vargas
Domínguez, S.
Bibcode: 2017RMxAC..49..150M
Altcode:
The Carrington Event was a spectacular blaze of light observed on
the solar surface on September 1, 1859, produced by intense activity
occurring in the Sun and having remarkable consequences on Earth,
e.g. extraordinary aurorae reported during the dawn on September
2th. The supreme solar-terrestrial event is the most energetic of which
we have records and the associated geomagnetic storm produced a major
auroral oval that expanded towards the equator of the planet. In this
work we show, based on historical evidence, that the associated aurorae
displayed in Montería, Colombia, at latitude 8° 45' N. We propose
that the location of the Earth's geomagnetic north pole, the lowest
in at least five centuries, added to the very energetic solar event,
allowed the aurora to reach such low latitudes.
Title: Tuning up Fuzzy Inference Systems by using optimization
algorithms for the classification of solar flares
Authors: Angélica Ramos Medina, Liz; Bustos Pinzón, Alex Francisco;
Melgarejo, Miguel A.; Vargas Domínguez, Santiago
Bibcode: 2017arXiv170608163A
Altcode:
In this work we describe the implementation and analysis of different
optimization algorithms used for finding the best set of parameters
for a Fuzzy Inference System intended to classify solar flares. The
parameters will be identified among a universe of possible solutions
for the algorithms, and the system will be tested in the particular
case of dealing with the aim of classifying the solar flares.
Title: Flare Energy Release in the Lower Solar Atmosphere near the
Magnetic Field Polarity Inversion Line
Authors: Sharykin, I. N.; Sadykov, V. M.; Kosovichev, A. G.; Vargas
Dominguez, S.; Zimovets, I. V.
Bibcode: 2017ApJ...840...84S
Altcode: 2018arXiv180104921S
We study flare processes in the solar atmosphere using observational
data for an M1-class flare of 2014 June 12, obtained by the New Solar
Telescope (NST/BBSO) and Helioseismic Magnetic Imager (HMI/SDO). The
main goal is to understand triggers and manifestations of the flare
energy release in the photosphere and chromosphere using high-resolution
optical observations and magnetic field measurements. We analyze
optical images, HMI Dopplergrams, and vector magnetograms, and use
nonlinear force-free field (NLFFF) extrapolations for reconstruction
of the magnetic topology and electric currents. The NLFFF modeling
reveals the interaction of two magnetic flux ropes with oppositely
directed magnetic fields in the polarity inversion line (PIL). These
flux ropes are observed as a compact sheared arcade along the PIL in the
high-resolution broadband continuum images from NST. In the vicinity of
the PIL, the NST {{H}}α observations reveal the formation of a thin
three-ribbon structure corresponding to a small-scale photospheric
magnetic arcade. The observational results are evidence in favor of
the primary energy release site located in the chromospheric plasma
with strong electric currents concentrated near the PIL. In this case,
magnetic reconnection is triggered by the interacting magnetic flux
ropes forming a current sheet elongated along the PIL.
Title: Multi-wavelength observations of vortex-like flows in the
photosphere using ground-based and space-borne telescopes
Authors: Palacios, J.; Vargas Domínguez, S.; Balmaceda, L. A.;
Cabello, I.; Domingo, V.
Bibcode: 2017arXiv170400660P
Altcode:
In this work we follow a series of papers on high-resolution
observations of small-scale structures in the solar atmosphere
\citep[][Cabello et al., in prep]{Balmaceda2009, Balmaceda2010,
Vargas2011, Palacios2012, Domingo2012, Vargas2015}, combining several
multi-wavelength data series. These were acquired by both ground-based
(SST) and space-borne (Hinode) instruments during the joint campaign of
the Hinode Operation Program 14, in September 2007. Diffraction-limited
SST data were taken in the G-band and G-cont, and were restored by
the MFBD technique. Hinode instruments, on the other hand, provided
multispectral data from SOT-FG in the CN band, and Mg~{\sc I} and
Ca {\sc II}~lines, as well as from SOT-SP in the Fe~{\sc I} line. In
this series of works we have thoroughly studied vortex flows and their
statistical occurrences, horizontal velocity fields by means of Local
Correlation Tracking (LCT), divergence and vorticity. Taking advantage
of the high-cadence and high spatial resolution data, we have also
studied bright point statistics and magnetic field intensification,
highlighting the importance of the smallest-scale magnetic element
observations.
Title: Development of a Homogenous Database of Bipolar Active Regions
Spanning Four Cycles
Authors: Munoz-Jaramillo, A.; Werginz, Z. A.; Vargas-Acosta, J. P.;
DeLuca, M. D.; Vargas-Dominguez, S.; Lamb, D. A.; DeForest, C. E.;
Longcope, D. W.; Martens, P.
Bibcode: 2016AGUFMSH11A2219M
Altcode:
The solar cycle can be understood as a process that alternates the
large-scale magnetic field of the Sun between poloidal and toroidal
configurations. Although the process that transitions the solar cycle
between toroidal and poloidal phases is still not fully understood,
theoretical studies, and observational evidence, suggest that this
process is driven by the emergence and decay of bipolar magnetic
regions (BMRs) at the photosphere. Furthermore, the emergence of
BMRs at the photosphere is the main driver behind solar variability
and solar activity in general; making the study of their properties
doubly important for heliospheric physics. However, in spite of their
critical role, there is still no unified catalog of BMRs spanning
multiple instruments and covering the entire period of systematic
measurement of the solar magnetic field (i.e. 1975 to present).In
this presentation we discuss an ongoing project to address this
deficiency by applying our Bipolar Active Region Detection (BARD)
code on full disk magnetograms measured by the 512 (1975-1993) and
SPMG (1992-2003) instruments at the Kitt Peak Vacuum Telescope (KPVT),
SOHO/MDI (1996-2011) and SDO/HMI (2010-present). First we will discuss
the results of our revitalization of 512 and SPMG KPVT data, then
we will discuss how our BARD code operates, and finally report the
results of our cross-callibration across instruments.The corrected
and improved KPVT magnetograms will be made available through the
National Solar Observatory (NSO) and Virtual Solar Observatory (VSO),
including updated synoptic maps produced by running the corrected KPVT
magnetograms though the SOLIS pipeline. The homogeneous active region
database will be made public by the end of 2017 once it has reached
a satisfactory level of quality and maturity. The Figure shows all
bipolar active regions present in our database (as of Aug 2016) colored
according to the instrument where they were detected. The image also
includes the names of the NSF-REU students in charge of the supervision
of the detection algorithm and the year in which they worked on the
catalog. Marker size is indicative of the total active region flux.
Title: The best of both worlds: Using automatic detection and limited
human supervision to create a homogenous magnetic catalog spanning
four solar cycles
Authors: Muñoz-Jaramillo, Andres; Werginz, Zachary; Vargas-Acosta,
Juan Pablo; DeLuca, Michael; Windmueller, J. C.; Zhang, Jie; Longcope,
Dana; Lamb, Derek; DeForest, Craig; Vargas-Domínguez, Santiago;
Harvey, Jack; Martens, Piet
Bibcode: 2016bida.conf.3194M
Altcode: 2022arXiv220311908M
Bipolar magnetic regions (BMRs) are the cornerstone of solar
variability. They are tracers of the large-scale magnetic processes
that give rise to the solar cycle, shapers of the solar corona,
building blocks of the large-scale solar magnetic field, and significant
contributors to the free-energetic budget that gives rise to flares and
coronal mass ejections. Surprisingly, no homogeneous catalog of BMRs
exists today, in spite of the existence of systematic measurements of
the magnetic field since the early 1970's. The purpose of this work is
to address this deficiency by creating a homogenous catalog of BMRs
from the 1970's until the present. For this purpose, in this paper
we discuss the strengths and weaknesses of the automatic and manual
detection of BMRs and how both methods can be combined to form the basis
of our Bipolar Active Region Detection (BARD) code and its supporting
human supervision module. At present, the BARD catalog contains more
than 10,000 unique BMRs tracked and characterized during every day
of their observation. Here we also discuss our future plans for the
creation of an extended multi-scale magnetic catalog combining the
SWAMIS and BARD catalogs.
Title: Relationship Between Chromospheric Evaporation and Magnetic
Field Topology in an M-Class Solar Flare
Authors: Sadykov, Viacheslav M.; Kosovichev, Alexander G.; Sharykin,
Ivan N.; Zimovets, Ivan V.; Vargas Dominguez, Santiago
Bibcode: 2016ApJ...828....4S
Altcode: 2016arXiv160405346S
Chromospheric evaporation is observed as Doppler blueshift during
solar flares. It plays a key role in the dynamics and energetics of
solar flares; however, its mechanism is still unknown. In this paper,
we present a detailed analysis of spatially resolved multi-wavelength
observations of chromospheric evaporation during an M 1.0-class
solar flare (SOL2014-06-12T21:12) using data from NASA’s Interface
Region Imaging Spectrograph and HMI/SDO (the Helioseismic and Magnetic
Imager on board the Solar Dynamics Observatory), and high-resolution
observations from VIS/NST (the Visible Imaging Spectrometer at the New
Solar Telescope). The results show that the averaged over the flare
region Fe xxi blueshift of the hot (107 K) evaporating
plasma is delayed relative to the C II redshift of the relatively
cold (104 K) chromospheric plasma by about one minute. The
spatial distribution of the delays is not uniform across the region
and can be as long as two minutes in several zones. Using vector
magnetograms from HMI, we reconstruct the magnetic field topology and
the quasi-separatrix layer, and find that the blueshift delay regions
as well as the Hα flare ribbons are connected to the region of the
magnetic polarity inversion line (PIL) and an expanding flux rope
via a system of low-lying loop arcades with a height of ≲4.5 Mm. As
a result, the chromospheric evaporation may be driven by the energy
release in the vicinity of PIL, and has the observed properties due
to a local magnetic field topology.
Title: VizieR Online Data Catalog: OGLE LC classification of MC
Cepheids (Garcia-Varela+, 2016)
Authors: Garcia-Varela, A.; Munoz, J. R.; Sabogal, B. E.; Vargas
Dominguez, S.; Martinez, J.
Bibcode: 2016yCat..18240074G
Altcode:
OGLE-II and OGLE-IV observations of Cepheid variables in the LMC and
SMC galaxies were collected with the 1.3m Warsaw telescope, at Las
Campanas Observatory, Chile (Udalski et al. 1999, J/AcA/49/223; 1999,
J/AcA/49/437; 2015AcA....65....1U). While Cepheid catalogs for the
OGLE-II fundamental mode contain 771 and 1319 stars for the LMC and
SMC, respectively, OGLE-IV has a nearly complete collection (2429 and
2739 for the LMC and SMC, respectively), covering practically the whole
Magellanic System with a time baseline of a little more than five years
(Soszynski et al. 2015AcA....65..329S). (1 data file).
Title: The Influential Effect of Blending, Bump, Changing Period,
and Eclipsing Cepheids on the Leavitt Law
Authors: García-Varela, A.; Muñoz, J. R.; Sabogal, B. E.; Vargas
Domínguez, S.; Martínez, J.
Bibcode: 2016ApJ...824...74G
Altcode: 2016arXiv160404814G
The investigation of the nonlinearity of the Leavitt law (LL) is a
topic that began more than seven decades ago, when some of the studies
in this field found that the LL has a break at about 10 days. The goal
of this work is to investigate a possible statistical cause of this
nonlinearity. By applying linear regressions to OGLE-II and OGLE-IV
data, we find that to obtain the LL by using linear regression, robust
techniques to deal with influential points and/or outliers are needed
instead of the ordinary least-squares regression traditionally used. In
particular, by using M- and MM-regressions we establish firmly and
without doubt the linearity of the LL in the Large Magellanic Cloud,
without rejecting or excluding Cepheid data from the analysis. This
implies that light curves of Cepheids suggesting blending, bumps,
eclipses, or period changes do not affect the LL for this galaxy. For
the Small Magellanic Cloud, when including Cepheids of this kind,
it is not possible to find an adequate model, probably because of the
geometry of the galaxy. In that case, a possible influence of these
stars could exist.
Title: Developing a Solar Magnetic Catalog Spanning Four Cycles
Authors: Werginz, Zachary; Munoz-Jaramillo, Andres; DeLuca, Michael
D.; Vargas Acosta, Juan Pablo; Vargas Dominguez, Santiago; Zhang,
Jie; Longcope, Dana; Martens, Petrus C.
Bibcode: 2016SPD....4740502W
Altcode:
Bipolar magnetic regions (BMRs) are the cornerstone of solar
cycle propagation, the building blocks that give structure to the
solar atmosphere, and the origin of the majority of space weather
events. However, in spite of their importance, there is no homogeneous
BMR catalog spanning the era of systematic solar magnetic field
measurements. Here we present the results of an ongoing project to
address this deficiency applying the Bipolar Active Region Detection
(BARD) code to magnetograms from the 512 Channel of the Kitt Peak Vaccum
Telescope, SOHO/MDI, and SDO/HMI.The BARD code automatically identifies
BMRs and tracks them as they are rotated by differential rotation. The
output of the automatic detection is supervised by a human observer
to correct possible mistakes made by the automatic algorithm (like
incorrect pairings and tracking mislabels). Extra passes are made to
integrate fragmented regions as well as to balance the flux between
BMR polarities. At the moment, our BMR database includes 6,885 unique
objects (detected and tracked) belonging to four separate solar cycles
(21-24).
Title: Observational Investigation of Energy Release in the Lower
Solar Atmosphere of a Solar Flare
Authors: Sharykin, I. N.; Sadykov, V. M.; Kosovichev, A. G.; Vargas
Dominguez, S.; Zimovets, I. V.
Bibcode: 2016arXiv160405380S
Altcode:
We study flare processes in the lower solar atmosphere using
observational data for a M1-class flare of June 12, 2014, obtained
by New Solar Telescope (NST/BBSO) and Helioseismic Magnetic Imager
(HMI/SDO). The main goal is to understand triggers and manifestations of
the flare energy release in the lower layers of the solar atmosphere
(the photosphere and chromosphere) using high-resolution optical
observations and magnetic field measurements. We analyze optical
images, HMI Dopplergrams and vector magnetograms, and use Non-Linear
Force-Free Field (NLFFF) extrapolations for reconstruction of the
magnetic topology. The NLFFF modelling reveals interaction of oppositely
directed magnetic flux-tubes in the PIL. These two interacting magnetic
flux tubes are observed as a compact sheared arcade along the PIL in the
high-resolution broad-band continuum images from NST. In the vicinity
of the PIL, the NST H alpha observations reveal formation of a thin
three-ribbon structure corresponding to the small-scale photospheric
magnetic arcade. Presented observational results evidence in favor of
location of the primary energy release site in the dense chromosphere
where plasma is partially ionized in the region of strong electric
currents concentrated near the polarity inversion line. Magnetic
reconnection may be triggered by two interacting magnetic flux tubes
with forming current sheet elongated along the PIL.
Title: Multi-wavelength Observations of Photospheric Vortex Flows
in the Photosphere Using Ground-based and Space-borne Telescopes
Authors: Palacios, J.; Vargas Domínguez, S.; Balmaceda, L. A.;
Cabello, I.; Domingo, V.
Bibcode: 2016ASPC..504..139P
Altcode:
In this work we follow a series of papers on high-resolution
observations of small-scale structures in the solar atmosphere
(Balmaceda et al. 2009, 2010; Vargas Domínguez et al. 2011; Palacios et
al. 2012; Domingo et al. 2012; Vargas Domínguez et al. 2015, Cabello et
al., in prep), combining several multi-wavelength data series. These
were acquired by both ground-based (SST) and space-borne (Hinode)
instruments during the joint campaign of the Hinode Operation Program
14, in September 2007. Diffraction-limited SST data were taken in the
G-band and G-cont, and were restored by the MFBD technique. Hinode
instruments, on the other hand, provided multispectral data from SOT-FG
in the CN band, and Mg I and Ca II lines, as well as from SOT-SP in
the Fe I line. In this series of works we have thoroughly studied
vortex flows and their statistical occurrences, horizontal velocity
fields by means of Local Correlation Tracking (LCT), divergence and
vorticity. Taking advantage of the high-cadence and high spatial
resolution data, we have also studied bright point statistics and
magnetic field intensification, highlighting the importance of the
smallest-scale magnetic element observations.
Title: Spectroscopic UV observations of M1.0 class solar flare from
IRIS satellite
Authors: Sadykov, Viacheslav M.; Kosovichev, Alexander G.; Sharykin,
Ivan N.; Vargas Dominguez, Santiago
Bibcode: 2016IAUS..320...64S
Altcode:
This work presents an analysis of UV spectroscopic observations from the
IRIS satellite of an M1.0 class flare occurred on 12 June 2014 in active
region NOAA 12087. Our analysis of the IRIS spectra and Slit-Jaw images
revealed presence of a strongly redshifted chromospheric jet before
the flare. We also found strong emission of the chromospheric lines,
and studied the C II 1334.5 Å line emission distribution in details. A
blueshift of the Fe XXI line across the flaring region corresponds to
evaporation flows of the hot chromospheric plasma with a speed of 50
km/s. Although the enhancement of the C II line integrated redshift
correlates with the flare X-ray emission, we classify the evaporation
as of a ``gentle'' type because of its long time scale and subsonic
velocities. Analysis of X-ray data from the RHESSI satellite showed that
both, an injection of accelerated particles and a heat flux from the
energy release site can explain the energetics of the observed event.
Title: The grand aurorae borealis seen in Colombia in 1859
Authors: Moreno Cárdenas, Freddy; Cristancho Sánchez, Sergio;
Vargas Domínguez, Santiago
Bibcode: 2016AdSpR..57..257M
Altcode: 2015arXiv150806365M; 2016AdSpR..57..257C
On Thursday, September 1, 1859, the British astronomer Richard
Carrington, for the first time ever, observes a spectacular gleam of
visible light on the surface of the solar disk, the photosphere. The
Carrington Event, as it is nowadays known by scientists, occurred
because of the high solar activity that had visible consequences
on Earth, in particular reports of outstanding aurorae activity
that amazed thousands of people in the western hemisphere during
the dawn of September 2. The geomagnetic storm, generated by the
solar-terrestrial event, had such a magnitude that the auroral oval
expanded towards the equator, allowing low latitudes, like Panama's
9°N, to catch a sight of the aurorae. An expedition was carried out
to review several historical reports and books from the northern
cities of Colombia allowed the identification of a narrative from
Montería, Colombia (8° 45‧N), that describes phenomena resembling
those of an aurorae borealis, such as fire-like lights, blazing and
dazzling glares, and the appearance of an immense S-like shape in
the sky. The very low latitude of the geomagnetic north pole in 1859,
the lowest value in over half a millennia, is proposed to have allowed
the observations of auroral events at locations closer to the equator,
and supports the historical description found in Colombia. The finding
of such chronicle represents one of the most complete descriptions of
low-latitude sightings of aurorae caused by the Carrington Event.
Title: Evolution of solar magnetic fields in a seismically active
region with recurrent flaring activity
Authors: Vargas Domínguez, S.; Buitrago Casas, J. C.; Molina, M.
Bibcode: 2015AGUFMSH13A2427V
Altcode:
In this work we investigate a solar active region NOAA 11515 with
flares and confirmed seismic activity. We focus on the evolution of
photospheric magnetic fields obtained from SDO/HMI data. Time series of
magnetograms allow the analysis of the evolution of magnetic features,
i.e changes in the magnetic geometry and magnetic flux. Moreover, we
follow the temporal evolution of white-light intensity to correlate
the flaring emission with the magnetic dynamics and th helioseismic
response. This study is intended to shed light on the evaluation of
different hypothesis of sunquakes generation.
Title: Contextualizing Solar Cycle 24: Report on the Development of
a Homogenous Database of Bipolar Active Regions Spanning Four Cycles
Authors: Munoz-Jaramillo, A.; Werginz, Z. A.; DeLuca, M. D.;
Vargas-Acosta, J. P.; Longcope, D. W.; Harvey, J. W.; Martens, P.;
Zhang, J.; Vargas-Dominguez, S.; DeForest, C. E.; Lamb, D. A.
Bibcode: 2015AGUFMSH33D..06M
Altcode:
The solar cycle can be understood as a process that alternates the
large-scale magnetic field of the Sun between poloidal and toroidal
configurations. Although the process that transitions the solar cycle
between toroidal and poloidal phases is still not fully understood,
theoretical studies, and observational evidence, suggest that this
process is driven by the emergence and decay of bipolar magnetic
regions (BMRs) at the photosphere. Furthermore, the emergence of
BMRs at the photosphere is the main driver behind solar variability
and solar activity in general; making the study of their properties
doubly important for heliospheric physics. However, in spite of their
critical role, there is still no unified catalog of BMRs spanning
multiple instruments and covering the entire period of systematic
measurement of the solar magnetic field (i.e. 1975 to present).In
this presentation we discuss an ongoing project to address this
deficiency by applying our Bipolar Active Region Detection (BARD)
code on full disk magnetograms measured by the 512 (1975-1993) and
SPMG (1992-2003) instruments at the Kitt Peak Vacuum Telescope (KPVT),
SOHO/MDI (1996-2011) and SDO/HMI (2010-present). First we will discuss
the results of our revitalization of 512 and SPMG KPVT data, then we
will discuss how our BARD code operates, and finally report the results
of our cross-callibration.The corrected and improved KPVT magnetograms
will be made available through the National Solar Observatory (NSO)
and Virtual Solar Observatory (VSO), including updated synoptic maps
produced by running the corrected KPVT magnetograms though the SOLIS
pipeline. The homogeneous active region database will be made public
by the end of 2017 once it has reached a satisfactory level of quality
and maturity. The Figure shows all bipolar active regions present in
our database (as of Aug 2015) colored according to the sign of their
leading polarity. Marker size is indicative of the total active region
flux. Anti-Hale regions are shown using solid markers.
Title: Python Implementation for Local Correlation Tracking Analysis
of Solar Data
Authors: Campos Rozo, J. I.; Vargas Domínguez, S.
Bibcode: 2015AGUFMSH43B2443C
Altcode:
The Local Correlation Tracking (LCT) technique is a robust method that
has been extensively applied to infer proper motions of structures
in time series of images. In solar physics research, LCT is a useful
tool to analyse the dynamics of plasma and the evolution of magnetic
fields in the solar atmosphere at different spatial and temporal
scales, among others (e.g granular and supergranular convective cells,
meridional flows, etc) SunPy is a joint effort of, using the advantages
of Python, developing tools to be applied for processing and analysis
of solar data. In this work, a widget implemented in Python and Sunpy
is developed, to generate a user-friendly graphical user interface
(GUI) to control various parameters for the process of calculating
flow maps of proper motions for a series of filtergrams.
Title: Parallel Evolution of Quasi-separatrix Layers and Active
Region Upflows
Authors: Mandrini, C. H.; Baker, D.; Démoulin, P.; Cristiani, G. D.;
van Driel-Gesztelyi, L.; Vargas Domínguez, S.; Nuevo, F. A.; Vásquez,
A. M.; Pick, M.
Bibcode: 2015ApJ...809...73M
Altcode: 2015arXiv150701264M
Persistent plasma upflows were observed with Hinode’s EUV
Imaging Spectrometer (EIS) at the edges of active region (AR)
10978 as it crossed the solar disk. We analyze the evolution of
the photospheric magnetic and velocity fields of the AR, model
its coronal magnetic field, and compute the location of magnetic
null-points and quasi-sepratrix layers (QSLs) searching for the origin
of EIS upflows. Magnetic reconnection at the computed null points
cannot explain all of the observed EIS upflow regions. However, EIS
upflows and QSLs are found to evolve in parallel, both temporarily
and spatially. Sections of two sets of QSLs, called outer and
inner, are found associated to EIS upflow streams having different
characteristics. The reconnection process in the outer QSLs is forced
by a large-scale photospheric flow pattern, which is present in the AR
for several days. We propose a scenario in which upflows are observed,
provided that a large enough asymmetry in plasma pressure exists
between the pre-reconnection loops and lasts as long as a photospheric
forcing is at work. A similar mechanism operates in the inner QSLs; in
this case, it is forced by the emergence and evolution of the bipoles
between the two main AR polarities. Our findings provide strong support
for the results from previous individual case studies investigating the
role of magnetic reconnection at QSLs as the origin of the upflowing
plasma. Furthermore, we propose that persistent reconnection along
QSLs does not only drive the EIS upflows, but is also responsible for
the continuous metric radio noise-storm observed in AR 10978 along
its disk transit by the Nançay Radio Heliograph.
Title: NST and IRIS multi-wavelength observations of an M1.0 class
solar flare
Authors: Vargas Domínguez, Santiago; Sadykov, Viacheslav; Kosovichev,
Alexander; Sharykin, Ivan; Struminsky, Alexei; Zimovets, Ivan
Bibcode: 2015IAUGA..2257574V
Altcode:
Although solar flares are the most energetic events in the Solar System
and have direct impact in the interplanetary space and ultimately
in our planet, there are still many unresolved issues concerning
their generation, the underlying processes of particle acceleration
involved, the effect at different layer in the solar atmosphere,
among others. This work presents new coordinated observations from the
New Solar Telescope (NST) and the space telescope IRIS that acquired
simultaneous observations of an M1.0 class flare occurred on 12 June,
2014 in active region NOAA 12087. NST filtergrams using the TiO filter,
together with chromospheric data from the Halpha line allow us to study
the evolution of the event from the first signs of the intensification
of the intensity in the region. We focused on a small portion where
the intensity enhancement in Halpha (blue and red wings) seems to be
triggered, and discovered a rapid expansion of a flux-rope structure
near the magnetic neutral line, in the sequence of high-resolution
photospheric images. IRIS observations evidenced strong emission of the
chromospheric and transition region lines during the flare. Jet-like
structures are detected before the initiation of the flare in
chromospheric lines and strong non-thermal emission in the transition
region at the beginning of the impulsive phase. Evaporation flows with
velocities up to 50 km/s occurred in the hot chromospheric plasma. We
interpreted the result in terms of the “gentle” evaporation that
occurs after accelerated particles heat the chromosphere.
Title: Properties of Chromospheric Evaporation and Plasma Dynamics
of a Solar Flare from Iris
Authors: Sadykov, Viacheslav M.; Vargas Dominguez, Santiago;
Kosovichev, Alexander G.; Sharykin, Ivan N.; Struminsky, Alexei B.;
Zimovets, Ivan
Bibcode: 2015ApJ...805..167S
Altcode: 2014arXiv1412.0172S
The dynamics of hot chromospheric plasma of solar flares is a
key to understanding the mechanisms of flare energy release and
particle acceleration. A moderate M1.0 class flare of 2014 June 12,
(SOL2014-06-12T21:12) was simultaneously observed by NASA's Interface
Region Imaging Spectrograph (IRIS) and other spacecraft, and also by
the New Solar Telescope at the BBSO. This paper presents the first
part of our investigation focused on analysis of the IRIS data. Our
analysis of the IRIS data in different spectral lines reveals a strong
redshifted jet-like flow with a speed of ∼100 km s-1 of the
chromospheric material before the flare. Strong nonthermal emission
of the C ii k 1334.5 Å line, formed in the chromosphere-corona
transition region, is observed at the beginning of the impulsive
phase in several small (with a size of ∼1″) points. It is also
found that the C ii k line is redshifted across the flaring region
before, during, and after the impulsive phase. A peak of integrated
emission of the hot (1.1 · 107 K) plasma in the Fe xxi
1354.1 Å line is detected approximately five minutes after the
integrated emission peak of the lower temperature C ii k. A strong
blueshift of the Fe xxi line across the flaring region corresponds to
evaporation flows of the hot chromospheric plasma with a speed of 50
km s-1. Additional analysis of the RHESSI data supports
the idea that the upper chromospheric dynamics observed by IRIS has
features of “gentle” evaporation driven by heating of the solar
chromosphere by accelerated electrons and by a heat flux from the
flare energy release site.
Title: Evolution of Small-Scale Magnetic Elements in the Vicinity
of Granular-Sized Swirl Convective Motions
Authors: Vargas Domínguez, S.; Palacios, J.; Balmaceda, L.; Cabello,
I.; Domingo, V.
Bibcode: 2015SoPh..290..301V
Altcode: 2014SoPh..tmp..187V; 2014arXiv1405.2380V
Advances in solar instrumentation have led to widespread use of time
series to study the dynamics of solar features, especially at small
spatial scales and at very fast cadences. Physical processes at such
scales are important as building blocks for many other processes
occurring from the lower to the upper layers of the solar atmosphere
and beyond, ultimately for understanding the larger picture of solar
activity. Ground-based (Swedish Solar Telescope) and space-borne
(Hinode) high-resolution solar data are analyzed in a quiet-Sun region
that displays negative-polarity small-scale magnetic concentrations
and a cluster of bright points observed in G-band. The region is
characterized by two granular-sized convective vortex-type plasma
motions, one of which appears to be affecting the dynamics of magnetic
features and bright points in its vicinity and is therefore the main
target of our investigations. We followed the evolution of the bright
points, intensity variations at different atmospheric height, and
the magnetic evolution for a set of interesting selected regions. We
describe the evolution of the photospheric plasma motions in the region
near the convective vortex and some plausible cases for convective
collapse detected in Stokes profiles.
Title: High-resolution Observations with New Solar Telescope
Authors: Vargas Domínguez, S.
Bibcode: 2014AGUFMSH31C..01V
Altcode:
Observations with the 1.6m aperture New Solar Telescope (NST) are
making next steps in our understanding of the structure and dynamics
of the solar surface structure with unprecedented spatial and temporal
resolutions. NST capabilities include the acquisition of filtergrams
in the photospheric broadband TiO 7075A line, narrow band images in
the HeI 10830A line and observations in the H-alpha 6563A line with the
Visible Imaging Spectrometer. Multi-wavelength observations allow us to
investigate the evolution of the solar atmosphere. The adaptive optics
correction system and the speckle image reconstruction processing
technique provide high resolution observations that are revealing
previously unresolved features in sunspots, i.e. fine structure of
oscillations and waves, penumbral jets, small-scale eruptions, and
accretion flows in a form of dense plasma sheets. Studies in less active
regions have evidenced the response of the solar atmosphere to the
emergence of small-scale magnetic flux. In particular we have detected
localized heating and plasma acceleration associated to the interaction
of the emerging and ambient magnetic fields. Such process may play a
significant role in the mass and energy flow from the interior to the
corona. The NST data are providing new observational insights that
are also crucial for testing advanced numerical simulations.
Title: Swirling motions, fast plasma flows and small-scale
chromospheric eruptions in a sunspot light-bridge
Authors: Vargas Domínguez, S.; Kosovichev, A. G.
Bibcode: 2014AGUFMSH41C4159V
Altcode:
Multi-wavelength observations with the 1.6m New Solar Telescope (NST)
at Big Bear Solar Observatory (BBSO) have evidenced a complex dynamics
of sunspots. We present photospheric and chromospheric observations
of a sunspot light-bridge in AR 11850 taken on 29 September 2013. The
NST/BFI data in the TiO reveal strong shearing and high-speed swirling
flows in the light-bridge. Scanning of the H-alpha spectral line shows
strong chromospheric downflows in the red wing near the outermost
part of the light-bridge. Chromospheric structuring around the spot
appears to be more complex due to the presence of the light-bridge. We
detect small-scale explosive events that are likely to be boosted by
the interactions of magnetic field lines at the chromospheric level
and therefore triggered by the evolution of the light bridge in the
photosphere beneath. In particular a very localized explosive event
reaching the transition region and coronal temperatures is observed
from simultaneous IRIS and SDO data.
Title: Multi-wavelength High-resolution Observations of a Small-scale
Emerging Magnetic Flux Event and the Chromospheric and Coronal
Response
Authors: Vargas Domínguez, Santiago; Kosovichev, Alexander;
Yurchyshyn, Vasyl
Bibcode: 2014ApJ...794..140V
Altcode: 2014arXiv1405.3550V
State-of-the-art solar instrumentation is now revealing magnetic
activity of the Sun with unprecedented temporal and spatial
resolutions. Observations with the 1.6 m aperture New Solar Telescope
(NST) of the Big Bear Solar Observatory are making next steps in our
understanding of the solar surface structure. Granular-scale magnetic
flux emergence and the response of the solar atmosphere are among the
key research topics of high-resolution solar physics. As part of a joint
observing program with NASA's Interface Region Imaging Spectrograph
(IRIS) mission on 2013 August 7, the NST observed active region
NOAA 11,810 in the photospheric TiO 7057 Å band with a resolution
of pixel size of 0.''034 and chromospheric He I 10830 Å and Hα
6563 Å wavelengths. Complementary data are provided by the Solar
Dynamics Observatory (SDO) and Hinode space-based telescopes. The
region displayed a group of solar pores, in the vicinity of which we
detect a small-scale buoyant horizontal magnetic flux tube causing
granular alignments and interacting with the preexisting ambient field
in the upper atmospheric layers. Following the expansion of distorted
granules at the emergence site, we observed a sudden appearance of an
extended surge in the He I 10830 Å data (bandpass of 0.05 Å). The
IRIS transition region imaging caught ejection of a hot plasma jet
associated with the He I surge. The SDO/HMI data used to study the
evolution of the magnetic and Doppler velocity fields reveal emerging
magnetic loop-like structures. Hinode/Ca II H and IRIS filtergrams
detail the connectivities of the newly emerged magnetic field in the
lower solar chromosphere. From these data, we find that the orientation
of the emerging magnetic field lines from a twisted flux tube formed
an angle of ~45° with the overlying ambient field. Nevertheless,
the interaction of emerging magnetic field lines with the pre-existing
overlying field generates high-temperature emission regions and boosts
the surge/jet production. The localized heating is detected before
and after the first signs of the surge/jet ejection. We compare the
results with previous observations and theoretical models and propose a
scenario for the activation of plasma jet/surges and confined heating
triggered by buoyant magnetic flux tubes rising up into a magnetized
upper environment. Such process may play a significant role in the
mass and energy flow from the interior to the corona.
Title: Recurrent Coronal Jets Induced by Magnetic Emergence in the
Solar Atmosphere
Authors: Guo, Y.; Démoulin, P.; Schmieder, B.; Ding, M. D.; Vargas
Domínguez, S.; Liu, Y.
Bibcode: 2014RMxAC..44...45G
Altcode:
Jets are part of the observed phenomenology in the solar corona. They
are thought to be a consequence of magnetic reconnection but the physics
involved is not completely understood. We study some recurrent jetting
events with unprecedented temporal and spatial resolutions.
Title: Transient Small-Scale Magnetic Flux Emergence and Atmospheric
Response Observed with New Solar Telescope and SDO
Authors: Vargas Domínguez, Santiago; Kosovichev, Alexander G.
Bibcode: 2014AAS...22412345V
Altcode:
State-of-the art solar instrumentation is now revealing the activity of
the Sun at the highest temporal and spatial resolution. Granular-scale
magnetic flux emergence and the response of the solar atmosphere is
one of the key topics. Observations with the 1.6m aperture New Solar
Telescope (NST) at Big Bear Solar Observatory (BBSO) are making next
steps in our understanding of the solar surface structure. On August 7,
2013, NST observed active region NOAA 11810 in different photospheric
and chromospheric wavelengths. The region displays a group of solar
pores, in the vicinity of which we detected a site of emerging magnetic
flux accompanied by intense and very confined abnormal granulation
dynamics, observed in the photospheric TiO 7057 A with a resolution
of 0.034 “/pix. Following the expansion of exploding granules in
this site, we observed a sudden appearance of an extended surge in the
HeI 10830A data (bandpass of 0.05 A). The SDO/HMI data used to study
the evolution of the magnetic field and Doppler velocities reveal a
short-lived emerging loop-like structure with strong upflows. We used
the SDO/AIA data to investigate the response of the transition region
and corona to the transient emerging flux phenomenon. We compare the
results with previous observations, and propose a scenario for the
production of plasma surges by the transient magnetic flux emergence
events.
Title: SunPy: Python for Solar Physics. An implementation for local
correlation tracking
Authors: Campos Rozo, J. I.; Vargas Dominguez, S.
Bibcode: 2014CEAB...38...67C
Altcode:
Python programming language has experienced a great progress and growing
use in the scientific community in the last years as well as a direct
impact on solar physics. Python is a very mature language and almost
any fundamental feature you might want to do is already implemented in
a library or module. SunPy is a common effort of, using the advantages
of Python, developing tools to be applied for processing and analysis
of solar data. In this work we present a particular development,
based on Python, for the analysis of proper motions in time series of
images through the local correlation tracking algorithm. A graphic user
interface allows to select different parameters for the computations,
visualization and analysis of flow fields.
Title: Emergence of a small-scale magnetic flux tube and the response
of the solar atmosphere
Authors: Vargas Dominguez, S.; Kosovichev, A. G.; Yurchyshyn, V.
Bibcode: 2014CEAB...38...25V
Altcode:
Cutting-edge observations with the 1.6-meter telescope at Big Bear
Solar Observatory (BBSO) in California have taken research into the
activity of the Sun to new levels of understanding of the structure
and evolution of the solar atmosphere at high-resolution spatial and
temporal scales. On August 7, 2013 the NST observed active region NOAA
11810 in photospheric and chromospheric wavelengths. The observations
were performed as part of a program conducted jointly with NASA's
Interface Region Imaging Spectrograph (IRIS) mission, Solar Dynamics
Observatory (SDO) and Hinode satellite. These observations provided a
unique view on the emergence of a buoyant small-scale magnetic-flux
rope in the solar photosphere. The event is accompanied by response
of the solar atmosphere once the newly emerged field interacts with
the pre-existing overlying one. The reconnection process that takes
place in the region produces jet emission and high-temperature points
in the chromosphere and corona.
Title: Twisting solar coronal jet launched at the boundary of an
active region
Authors: Schmieder, B.; Guo, Y.; Moreno-Insertis, F.; Aulanier, G.;
Yelles Chaouche, L.; Nishizuka, N.; Harra, L. K.; Thalmann, J. K.;
Vargas Dominguez, S.; Liu, Y.
Bibcode: 2013A&A...559A...1S
Altcode: 2013arXiv1309.6514S
Aims: A broad jet was observed in a weak magnetic field area
at the edge of active region NOAA 11106 that also produced other
nearby recurring and narrow jets. The peculiar shape and magnetic
environment of the broad jet raised the question of whether it was
created by the same physical processes of previously studied jets
with reconnection occurring high in the corona.
Methods:
We carried out a multi-wavelength analysis using the EUV images
from the Atmospheric Imaging Assembly (AIA) and magnetic fields
from the Helioseismic and Magnetic Imager (HMI) both on-board the
Solar Dynamics Observatory, which we coupled to a high-resolution,
nonlinear force-free field extrapolation. Local correlation tracking
was used to identify the photospheric motions that triggered the jet,
and time-slices were extracted along and across the jet to unveil its
complex nature. A topological analysis of the extrapolated field was
performed and was related to the observed features.
Results:
The jet consisted of many different threads that expanded in around 10
minutes to about 100 Mm in length, with the bright features in later
threads moving faster than in the early ones, reaching a maximum speed
of about 200 km s-1. Time-slice analysis revealed a striped
pattern of dark and bright strands propagating along the jet, along with
apparent damped oscillations across the jet. This is suggestive of a
(un)twisting motion in the jet, possibly an Alfvén wave. Bald patches
in field lines, low-altitude flux ropes, diverging flow patterns, and a
null point were identified at the basis of the jet.
Conclusions:
Unlike classical λ or Eiffel-tower-shaped jets that appear to be caused
by reconnection in current sheets containing null points, reconnection
in regions containing bald patches seems to be crucial in triggering
the present jet. There is no observational evidence that the flux
ropes detected in the topological analysis were actually being ejected
themselves, as occurs in the violent phase of blowout jets; instead,
the jet itself may have gained the twist of the flux rope(s) through
reconnection. This event may represent a class of jets different from
the classical quiescent or blowout jets, but to reach that conclusion,
more observational and theoretical work is necessary.
Title: Recurrent coronal jets induced by repetitively accumulated
electric currents
Authors: Guo, Y.; Démoulin, P.; Schmieder, B.; Ding, M. D.; Vargas
Domínguez, S.; Liu, Y.
Bibcode: 2013A&A...555A..19G
Altcode: 2013arXiv1305.0902G
Context. Jets of plasma are frequently observed in the solar corona. A
self-similar recurrent behavior is observed in a fraction of them.
Aims: Jets are thought to be a consequence of magnetic reconnection;
however, the physics involved is not fully understood. Therefore,
we study some jet observations with unprecedented temporal and
spatial resolutions.
Methods: The extreme-ultraviolet (EUV)
jets were observed by the Atmospheric Imaging Assembly on board the
Solar Dynamics Observatory (SDO). The Helioseismic and Magnetic Imager
(HMI) on board SDO measured the vector magnetic field, from which
we derive the magnetic flux evolution, the photospheric velocity
field, and the vertical electric current evolution. The magnetic
configuration before the jets is derived by the nonlinear force-free
field extrapolation.
Results: Three EUV jets recurred in about
one hour on 17 September 2010 in the following magnetic polarity
of active region 11106. We derive that the jets are above a pair of
parasitic magnetic bipoles that are continuously driven by photospheric
diverging flows. The interaction drove the buildup of electric currents,
which we observed as elongated patterns at the photospheric level. For
the first time, the high temporal cadence of the HMI allows the
evolution of such small currents to be followed. In the jet region,
we found that the integrated absolute current peaks repetitively in
phase with the 171 Å flux evolution. The current buildup and its
decay are both fast, about ten minutes each, and the current maximum
precedes the 171 Å also by about ten minutes. Then, the HMI temporal
cadence is marginally fast enough to detect such changes.
Conclusions: The photospheric current pattern of the jets is found to
be associated with the quasi-separatrix layers deduced from the magnetic
extrapolation. From previous theoretical results, the observed diverging
flows are expected to continuously build such currents. We conclude
that the magnetic reconnection occurs periodically, in the current
layer created between the emerging bipoles and the large-scale active
region field. The periodic magnetic reconnection induced the observed
recurrent coronal jets and the decrease of the vertical electric
current magnitude. Two movies are available in electronic form
at http://www.aanda.org
Title: On the response of the solar atmosphere to small-scale magnetic
flux emergence
Authors: Vargas Dominguez, Santiago; van Driel-Gesztelyi, Lidia
Bibcode: 2013EGUGA..15..925V
Altcode:
In this work we analyze data from the Hinode spacecraft targeting
an emerging magnetic flux region. We focus on small-scale events
identified by distinctive dark features in CaII H chromospheric
filtergrams. Energy release at low chromospheric heights is detected
to be boosted by the disappearance of the dark features after they
reached their maximum size. The observed phenomena are explained as
evidencing elementary flux emergence into the solar atmosphere. We
are thus detecting granular-scale arch filament systems, that emerge
and interact with pre-existing fields. The results give new insights
on the resistive flux emergence scenario driving the configuration
and evolution of solar active regions. We compare the results with
emergence of individual magnetic loops seen in quiet sun regions.
Title: Nonlinear Force-Free Extrapolation of Emerging Flux with a
Global Twist and Serpentine Fine Structures
Authors: Valori, G.; Green, L. M.; Démoulin, P.; Vargas Domínguez,
S.; van Driel-Gesztelyi, L.; Wallace, A.; Baker, D.; Fuhrmann, M.
Bibcode: 2012SoPh..278...73V
Altcode:
We study the flux emergence process in NOAA active region 11024, between
29 June and 7 July 2009, by means of multi-wavelength observations
and nonlinear force-free extrapolation. The main aim is to extend
previous investigations by combining, as much as possible, high spatial
resolution observations to test our present understanding of small-scale
(undulatory) flux emergence, whilst putting these small-scale events
in the context of the global evolution of the active region. The
combination of these techniques allows us to follow the whole process,
from the first appearance of the bipolar axial field on the east limb,
until the buoyancy instability could set in and raise the main body
of the twisted flux tube through the photosphere, forming magnetic
tongues and signatures of serpentine field, until the simplification
of the magnetic structure into a main bipole by the time the active
region reaches the west limb. At the crucial time of the main emergence
phase high spatial resolution spectropolarimetric measurements of the
photospheric field are employed to reconstruct the three-dimensional
structure of the nonlinear force-free coronal field, which is then
used to test the current understanding of flux emergence processes. In
particular, knowledge of the coronal connectivity confirms the identity
of the magnetic tongues as seen in their photospheric signatures,
and it exemplifies how the twisted flux, which is emerging on small
scales in the form of a sea-serpent, is subsequently rearranged by
reconnection into the large-scale field of the active region. In
this way, the multi-wavelength observations combined with a nonlinear
force-free extrapolation provide a coherent picture of the emergence
process of small-scale magnetic bipoles, which subsequently reconnect
to form a large-scale structure in the corona.
Title: Granular-Scale Elementary Flux Emergence Episodes in a Solar
Active Region
Authors: Vargas Domínguez, S.; van Driel-Gesztelyi, L.; Bellot Rubio,
L. R.
Bibcode: 2012SoPh..278...99V
Altcode: 2012SoPh..tmp..259F; 2012arXiv1203.6428V
We analyse data from Hinode spacecraft taken over two 54-minute periods
during the emergence of AR 11024. We focus on small-scale portions
within the observed solar active region and discover the appearance of
very distinctive small-scale and short-lived dark features in Ca II H
chromospheric filtergrams and Stokes I images. The features appear in
regions with close-to-zero longitudinal magnetic field, and are observed
to increase in length before they eventually disappear. Energy release
in the low chromospheric line is detected while the dark features
are fading. Three complete series of these events are detected with
remarkably similar properties, i.e. lifetime of ≈ 12 min, maximum
length and area of 2 - 4 Mm and 1.6 - 4 Mm2, respectively,
and all with associated brightenings. In time series of magnetograms a
diverging bipolar configuration is observed accompanying the appearance
of the dark features and the brightenings. The observed phenomena
are explained as evidencing elementary flux emergence in the solar
atmosphere, i.e. small-scale arch filament systems rising up from the
photosphere to the lower chromosphere with a length scale of a few
solar granules. Brightenings are explained as being the signatures of
chromospheric heating triggered by reconnection of the rising loops
(once they have reached chromospheric heights) with pre-existing
magnetic fields, as well as being due to reconnection/cancellation
events in U-loop segments of emerging serpentine fields. The
characteristic length scale, area and lifetime of these elementary
flux emergence events agree well with those of the serpentine field
observed in emerging active regions. We study the temporal evolution
and dynamics of the events and compare them with the emergence of
magnetic loops detected in quiet Sun regions and serpentine flux
emergence signatures in active regions. The physical processes of
the emergence of granular-scale magnetic loops seem to be the same
in the quiet Sun and active regions. The difference is the reduced
chromospheric emission in the quiet Sun attributed to the fact that
loops are emerging in a region of lower ambient magnetic field density,
making interactions and reconnection less likely to occur. Incorporating
the novel features of granular-scale flux emergence presented in this
study, we advance the scenario for serpentine flux emergence.
Title: On Signatures of Twisted Magnetic Flux Tube Emergence
Authors: Vargas Domínguez, S.; MacTaggart, D.; Green, L.; van
Driel-Gesztelyi, L.; Hood, A. W.
Bibcode: 2012SoPh..278...33V
Altcode: 2011arXiv1105.0758V
Recent studies of NOAA active region 10953, by Okamoto et
al. (Astrophys. J. Lett.673, 215, 2008; Astrophys. J.697, 913, 2009),
have interpreted photospheric observations of changing widths of the
polarities and reversal of the horizontal magnetic field component as
signatures of the emergence of a twisted flux tube within the active
region and along its internal polarity inversion line (PIL). A filament
is observed along the PIL and the active region is assumed to have an
arcade structure. To investigate this scenario, MacTaggart and Hood
(Astrophys. J. Lett.716, 219, 2010) constructed a dynamic flux emergence
model of a twisted cylinder emerging into an overlying arcade. The
photospheric signatures observed by Okamoto et al. (2008, 2009) are
present in the model although their underlying physical mechanisms
differ. The model also produces two additional signatures that can be
verified by the observations. The first is an increase in the unsigned
magnetic flux in the photosphere at either side of the PIL. The second
is the behaviour of characteristic photospheric flow profiles associated
with twisted flux tube emergence. We look for these two signatures in
AR 10953 and find negative results for the emergence of a twisted flux
tube along the PIL. Instead, we interpret the photospheric behaviour
along the PIL to be indicative of photospheric magnetic cancellation
driven by flows from the dominant sunspot. Although we argue against
flux emergence within this particular region, the work demonstrates
the important relationship between theory and observations for the
successful discovery and interpretation of signatures of flux emergence.
Title: Magnetic Topology of a Naked Sunspot: Is It Really Naked?
Authors: Sainz Dalda, A.; Vargas Domínguez, S.; Tarbell, T. D.
Bibcode: 2012ApJ...746L..13S
Altcode: 2012arXiv1202.0591S
The high spatial, temporal, and spectral resolution achieved by Hinode
instruments gives much better understanding of the behavior of some
elusive solar features, such as pores and naked sunspots. Their fast
evolution and, in some cases, their small sizes have made their study
difficult. The moving magnetic features (MMFs) have been studied during
the last 40 years. They have been always associated with sunspots,
especially with the penumbra. However, a recent observation of a naked
sunspot (one with no penumbra) has shown MMF activity. The authors
of this reported observation expressed their reservations about the
explanation given to the bipolar MMF activity as an extension of the
penumbral filaments into the moat. How can this type of MMF exist when
a penumbra does not? In this Letter, we study the full magnetic and
(horizontal) velocity topology of the same naked sunspot, showing how
the existence of a magnetic field topology similar to that observed
in sunspots can explain these MMFs, even when the intensity map of
the naked sunspot does not show a penumbra.
Title: Magnetic field emergence in mesogranular-sized exploding
granules observed with sunrise/IMaX data
Authors: Palacios, J.; Blanco Rodríguez, J.; Vargas Domínguez, S.;
Domingo, V.; Martínez Pillet, V.; Bonet, J. A.; Bellot Rubio, L. R.;
Del Toro Iniesta, J. C.; Solanki, S. K.; Barthol, P.; Gandorfer, A.;
Berkefeld, T.; Schmidt, W.; Knölker, M.
Bibcode: 2012A&A...537A..21P
Altcode: 2011arXiv1110.4555P
We report on magnetic field emergences covering significant
areas of exploding granules. The balloon-borne mission Sunrise
provided high spatial and temporal resolution images of the solar
photosphere. Continuum images, longitudinal and transverse magnetic
field maps and Dopplergrams obtained by IMaX onboard Sunrise are
analyzed by local correlation traking (LCT), divergence calculation
and time slices, Stokes inversions and numerical simulations are also
employed. We characterize two mesogranular-scale exploding granules
where ~1018 Mx of magnetic flux emerges. The emergence
of weak unipolar longitudinal fields (~100 G) start with a single
visible magnetic polarity, occupying their respective granules' top
and following the granular splitting. After a while, mixed polarities
start appearing, concentrated in downflow lanes. The events last around
20 min. LCT analyses confirm mesogranular scale expansion, displaying
a similar pattern for all the physical properties, and divergence
centers match between all of them. We found a similar behaviour
with the emergence events in a numerical MHD simulation. Granule
expansion velocities are around 1 kms-1 while magnetic
patches expand at 0.65 kms-1. One of the analyzed events
evidences the emergence of a loop-like structure. Advection of
the emerging magnetic flux features is dominated by convective
motion resulting from the exploding granule due to the magnetic
field frozen in the granular plasma. Intensification of the
magnetic field occurs in the intergranular lanes, probably
because of being directed by the downflowing plasma. Movies
associated to Figs. 2-4 are available in electronic form at http://www.aanda.org
Title: Spatial distribution and statistical properties of small-scale
convective vortex-like motions in a quiet-Sun region
Authors: Vargas Domínguez, S.; Palacios, J.; Balmaceda, L.; Cabello,
I.; Domingo, V.
Bibcode: 2011MNRAS.416..148V
Altcode: 2011MNRAS.tmp.1046V; 2011arXiv1105.3092V
High-resolution observations of a quiet-Sun internetwork region taken
with the Solar 1-m Swedish Telescope in La Palma are analysed. We
determine the location of small-scale vortex motions in the solar
photospheric region by computing the horizontal proper motions
of small-scale structures on time-series of images. These plasma
convectively driven swirl motions are associated to (1) downdrafts
(that have been commonly explained as corresponding to sites where
the plasma is cooled down and hence returned to the interior below
the visible photospheric level) and (2) horizontal velocity vectors
converging on a central point. The sink cores are proved to be the final
destination of passive floats tracing plasma flows towards the centre
of each vortex. We establish the occurrence of these events to be 1.4
× 10-3 and 1.6 × 10-3 vortices Mm-2
min-1, respectively, for the two time-series analysed here.
Title: Spectropolarimetric Study of Sea-serpent Penumbral Filaments
and a Naked Sunspot
Authors: Sainz Dalda, Alberto; Tarbell, T.; Title, A.; Vargas
Dominguez, S.; Bellot Rubio, L. R.
Bibcode: 2011SPD....42.0303S
Altcode: 2011BAAS..43S.0303S
We present a spectropolarimetric study of the sea-serpent penumbral
filaments in AR NOAA 10944 and of a naked sunspot (i.e. a sunspot-like
feature without penumbra) in AR NOAA 10977. Both active regions were
observed by Hinode-SOT/SP in the photospheric lines Fe I 6301 &
6302 [[Unable to Display Character: Ǻ]]. The high spatial and
temporal resolution combined with the high polarimetric sensitivity
of these observations enables us to get a better understanding of the
dynamics of the penumbra and the moving magnetic feature (herafter MMF)
activity in and around both traditional and naked sunspots. Our results
show how the temporal evolution of the sea-serpent filaments fits
very well with the thin-tube flux model for the penumbra presented by
Schlichenmaier (2003). In addition, the spectropolarmetric analysis of
the naked sunspot addresses the issue posed by Zuccarello et al. (2009)
about the existence of bipolar MMFs around naked sunspots even when
they cannot be explained as an extension of the penumbral filaments.
Title: The Imaging Magnetograph eXperiment (IMaX) for the Sunrise
Balloon-Borne Solar Observatory
Authors: Martínez Pillet, V.; del Toro Iniesta, J. C.;
Álvarez-Herrero, A.; Domingo, V.; Bonet, J. A.; González Fernández,
L.; López Jiménez, A.; Pastor, C.; Gasent Blesa, J. L.; Mellado, P.;
Piqueras, J.; Aparicio, B.; Balaguer, M.; Ballesteros, E.; Belenguer,
T.; Bellot Rubio, L. R.; Berkefeld, T.; Collados, M.; Deutsch, W.;
Feller, A.; Girela, F.; Grauf, B.; Heredero, R. L.; Herranz, M.;
Jerónimo, J. M.; Laguna, H.; Meller, R.; Menéndez, M.; Morales, R.;
Orozco Suárez, D.; Ramos, G.; Reina, M.; Ramos, J. L.; Rodríguez,
P.; Sánchez, A.; Uribe-Patarroyo, N.; Barthol, P.; Gandorfer, A.;
Knoelker, M.; Schmidt, W.; Solanki, S. K.; Vargas Domínguez, S.
Bibcode: 2011SoPh..268...57M
Altcode: 2010SoPh..tmp..181M; 2010arXiv1009.1095M
The Imaging Magnetograph eXperiment (IMaX) is a spectropolarimeter
built by four institutions in Spain that flew on board the Sunrise
balloon-borne solar observatory in June 2009 for almost six days over
the Arctic Circle. As a polarimeter, IMaX uses fast polarization
modulation (based on the use of two liquid crystal retarders),
real-time image accumulation, and dual-beam polarimetry to reach
polarization sensitivities of 0.1%. As a spectrograph, the instrument
uses a LiNbO3 etalon in double pass and a narrow band
pre-filter to achieve a spectral resolution of 85 mÅ. IMaX uses the
high-Zeeman-sensitive line of Fe I at 5250.2 Å and observes all four
Stokes parameters at various points inside the spectral line. This
allows vector magnetograms, Dopplergrams, and intensity frames to be
produced that, after reconstruction, reach spatial resolutions in the
0.15 - 0.18 arcsec range over a 50×50 arcsec field of view. Time
cadences vary between 10 and 33 s, although the shortest one only
includes longitudinal polarimetry. The spectral line is sampled in
various ways depending on the applied observing mode, from just two
points inside the line to 11 of them. All observing modes include
one extra wavelength point in the nearby continuum. Gauss equivalent
sensitivities are 4 G for longitudinal fields and 80 G for transverse
fields per wavelength sample. The line-of-sight velocities are estimated
with statistical errors of the order of 5 - 40 m s−1. The
design, calibration, and integration phases of the instrument,
together with the implemented data reduction scheme, are described in
some detail.
Title: Multiwavelength Observations of Small-scale Reconnection
Events Triggered by Magnetic Flux Emergence in the Solar Atmosphere
Authors: Guglielmino, S. L.; Bellot Rubio, L. R.; Zuccarello, F.;
Aulanier, G.; Vargas Domínguez, S.; Kamio, S.
Bibcode: 2010ApJ...724.1083G
Altcode: 2010arXiv1007.4657G
The interaction between emerging magnetic flux and the pre-existing
ambient field has become a "hot" topic for both numerical simulations
and high-resolution observations of the solar atmosphere. The appearance
of brightenings and surges during episodes of flux emergence is believed
to be a signature of magnetic reconnection processes. We present an
analysis of a small-scale flux emergence event in NOAA 10971, observed
simultaneously with the Swedish 1 m Solar Telescope on La Palma and the
Hinode satellite during a joint campaign in 2007 September. Extremely
high-resolution G-band, Hα, and Ca II H filtergrams, Fe I and Na
I magnetograms, EUV raster scans, and X-ray images show that the
emerging region was associated with chromospheric, transition region
and coronal brightenings, as well as with chromospheric surges. We
suggest that these features were caused by magnetic reconnection
at low altitude in the atmosphere. To support this idea, we perform
potential and linear force-free field extrapolations using the FROMAGE
service. The extrapolations show that the emergence site is cospatial
with a three-dimensional null point, from which a spine originates. This
magnetic configuration and the overall orientation of the field lines
above the emerging flux region are compatible with the structures
observed in the different atmospheric layers and remain stable against
variations of the force-free field parameter. Our analysis supports
the predictions of recent three-dimensional numerical simulations that
energetic phenomena may result from the interaction between emerging
flux and the pre-existing chromospheric and coronal field.
Title: Retrieval of solar magnetic fields from high-spatial resolution
filtergraph data: the Imaging Magnetograph eXperiment (IMaX)
Authors: Orozco Suárez, D.; Bellot Rubio, L. R.; Martínez Pillet,
V.; Bonet, J. A.; Vargas Domínguez, S.; Del Toro Iniesta, J. C.
Bibcode: 2010A&A...522A.101O
Altcode: 2010arXiv1006.5510O
Context. The design of modern instruments does not only imply thorough
studies of instrumental effects but also a good understanding of the
scientific analysis planned for the data.
Aims: We investigate
the reliability of Milne-Eddington (ME) inversions of high-resolution
magnetograph measurements such as those to be obtained with the Imaging
Magnetograph eXperiment (IMaX) aboard the Sunrise balloon. We also
provide arguments to choose either Fe I 525.02 or 525.06 nm as the
most suitable line for IMaX.
Methods: We reproduce an IMaX
observation using magnetoconvection simulations of the quiet Sun
and synthesizing the four Stokes profiles emerging from them. The
profiles are degraded by spatial and spectral resolution, noise,
and limited wavelength sampling, just as real IMaX measurements. We
invert these data and estimate the uncertainties in the retrieved
physical parameters caused by the ME approximation and the spectral
sampling.
Results: It is possible to infer the magnetic field
strength, inclination, azimuth, and line-of-sight velocity from
standard IMaX measurements (4 Stokes parameters, 5 wavelength points,
and a signal-to-noise ratio of 1000) applying ME inversions to any
of the Fe I lines at 525 nm. We also find that telescope diffraction
has important effects on the spectra coming from very high resolution
observations of inhomogeneous atmospheres. Diffration reduces the
amplitude of the polarization signals and changes the asymmetry of
the Stokes profiles.
Conclusions: The two Fe I lines at 525 nm
meet the scientific requirements of IMaX, but Fe I 525.02 nm is to be
preferred because it leads to smaller uncertainties in the retrieved
parameters and offers a better detectability of the weakest (linear)
polarization signals prevailing in the quiet Sun.
Title: Characterization of horizontal flows around solar pores from
high-resolution time series of images
Authors: Vargas Domínguez, S.; de Vicente, A.; Bonet, J. A.; Martínez
Pillet, V.
Bibcode: 2010A&A...516A..91V
Altcode: 2010arXiv1003.2134V
Context. Though there is increasing evidence linking the moat flow and
the Evershed flow along the penumbral filaments, there is not a clear
consensus regarding the existence of a moat flow around umbral cores
and pores, and the debate is still open. Solar pores appear to be a
suitable scenario to test the moat-penumbra relation as they correspond
to a direct interaction between the umbra and the convective plasma
in the surrounding photosphere without any intermediate structure in
between.
Aims: We study solar pores based on high-resolution
ground-based and satellite observations.
Methods: Local
correlation tracking techniques were applied to different-duration
time series to analyze the horizontal flows around several solar
pores.
Results: Our results establish that the flows calculated
from different solar pore observations are coherent among each other
and show the determining and overall influence of exploding events in
the granulation around the pores. We do not find any sign of moat-like
flows surrounding solar pores, but a clearly defined region of inflows
surrounding them.
Conclusions: The connection between moat
flows and flows associated to penumbral filaments is hereby reinforced.
Title: Evidence of small-scale magnetic concentrations dragged by
vortex motion of solar photospheric plasma
Authors: Balmaceda, L.; Vargas Domínguez, S.; Palacios, J.; Cabello,
I.; Domingo, V.
Bibcode: 2010A&A...513L...6B
Altcode: 2010arXiv1004.1185B
Vortex-type motions have been measured by tracking bright points in
high-resolution observations of the solar photosphere. These small-scale
motions are thought to be determinant in the evolution of magnetic
footpoints and their interaction with plasma and therefore likely to
play a role in heating the upper solar atmosphere by twisting magnetic
flux tubes. We report the observation of magnetic concentrations being
dragged towards the center of a convective vortex motion in the solar
photosphere from high-resolution ground-based and space-borne data. We
describe this event by analyzing a series of images at different solar
atmospheric layers. By computing horizontal proper motions, we detect a
vortex whose center appears to be the draining point for the magnetic
concentrations detected in magnetograms and well-correlated with the
locations of bright points seen in G-band and CN images.
Title: High-resolution observations of interactions during the
emergence of magnetic flux from the photosphere to the corona
Authors: Guglielmino, S. L.; Bellot Rubio, L. R.; Zuccarello, F.;
Romano, P.; Vargas Domínguez, S.
Bibcode: 2010MSAIS..14..184G
Altcode:
Interactions occurring at sites where new flux emerges and an
old flux system is already present can trigger various phenomena,
such as flux cancellation, reconnection events, and even flaring. We
analyze high-resolution observations of a small-scale flux emergence
event in NOAA 10971, observed simultaneously by the Hinode satellite
and the Swedish Solar Telescope in La Palma Island during a joint
campaign. G-band, Halpha , and Ca II H filtergrams were acquired
together with Fe I and Na I magnetograms. The data show that the
emerging region seen in the photosphere is associated with Ca II H
brightenings and a Halpha chromospheric surge. Moreover, EUV raster
scans and XRT filtergrams show cospatial brightenings. Comparing our
results with recent 3D simulations, we interpret our observations in the
context of the low-altitude magnetic reconnection model, suggesting
that interactions between the emerging flux and the pre-existing
magnetic field can explain the observed coupling.
Title: Study of horizontal flows in solar active regions based on
high-resolution image reconstruction techniques
Authors: Vargas Dominguez, S.
Bibcode: 2009PhDT........78V
Altcode: 2009arXiv0906.0336V
This thesis can be framed in a more general concept designated as
"High resolution in solar physics". The first part of the thesis
is dedicated to the topic of high-resolution observations and image
restoration. It begins with a theoretical reviewing of the problem that
represents the atmospheric turbulence and the instrumental aberrations
on the image quality. This problem force us to implement post-facto
image restoration techniques that, added to the real-time corrections
performed by the Adaptive Optics, gives us images closer to reality. To
have good solar observations overcoming the negative influence of the
Earth' s atmosphere, one effort is being made with the development of
the Sunrise mission. This project consists in a balloon-borne mission
that will launch a 1-m telescope to the stratosphere and will record
data with unprecedented temporal, spatial and spectral resolution. The
main aim of Sunrise is to study the formation of magnetic structures in
the solar atmosphere and their interaction with the convective plasma
flows. The on-board instrument Imaging Magnetograph eXperiment (IMaX)
will be able to produce magnetic field maps of extensive solar regions
by measuring the light polarization in certain spectral lines. As
a member of the IMaX team, I have developed an in-flight calibration
method to characterize the aberrations affecting the images in IMaX. The
second part of the thesis is centered on the study of horizontal flows
in solar active regions. Data from ground-based and space observations
are used as well as reconstruction techniques to restore the images. We
focus on the proper motions of structures in and around solar active
regions. The way to quantify the horizontal flows in the field-of-view
consist of using local correlation tracking techniques that generate
flow maps.
Title: Estudio de flujos horizontales en regiones solares activas
basado en técnicas de alta resolución para reconstrucción de
imágenes Title: Estudio de flujos horizontales en regiones solares
activas basado en técnicas de alta resolución para reconstrucción
de imágenes Title: Study of horizontal flows in solar active regions
based on high-resolution techniques for image reconstruction;
Authors: Vargas Domínguez, Santiago
Bibcode: 2009PhDT.......113V
Altcode:
No abstract at ADS
Title: Moat Flow in the Vicinity of Sunspots for Various Penumbral
Configurations
Authors: Vargas Domínguez, S.; Rouppe van der Voort, L.; Bonet,
J. A.; Martínez Pillet, V.; Van Noort, M.; Katsukawa, Y.
Bibcode: 2008ApJ...679..900V
Altcode: 2008arXiv0802.1457V
High-resolution time series of sunspots have been obtained with
the Swedish 1 m Solar Telescope between 2003 and 2006 at different
locations on the solar disk. Proper motions in seven different active
regions have been studied. The analysis was performed by applying local
correlation tracking to every series of sunspots, each of them more than
40 minutes long. The sunspots' shapes include a different variety of
penumbral configurations. We report on the systematic behavior of the
large-scale outflows surrounding the sunspots, commonly known as moat
flows, that are essentially present only when preceded by a penumbra
not tangential but perpendicular to the sunspot border. We present
one case for which this rule appears not to be confirmed. We speculate
that the magnetic neutral line, which is located in the vicinity of the
anomalous region, might be responsible for blocking the outflow. These
new results confirm the systematic and strong relation between the
moat flows and the existence of penumbrae. A comparative statistical
study between moats and standard granulation is also performed.
Title: Relationships between magnetic foot points and G-band bright
structures
Authors: Ishikawa, R.; Tsuneta, S.; Kitakoshi, Y.; Katsukawa, Y.;
Bonet, J. A.; Vargas Domínguez, S.; Rouppe van der Voort, L. H. M.;
Sakamoto, Y.; Ebisuzaki, T.
Bibcode: 2007A&A...472..911I
Altcode: 2008arXiv0802.1765I
Aims:Magnetic elements are thought to be described by flux tube models,
and are well reproduced by MHD simulations. However, these simulations
are only partially constrained by observations. We observationally
investigate the relationship between G-band bright points and magnetic
structures to clarify conditions, which make magnetic structures
bright in G-band.
Methods: The G-band filtergrams together with
magnetograms and dopplergrams were taken for a plage region covered
by abnormal granules as well as ubiquitous G-band bright points,
using the Swedish 1-m Solar Telescope (SST) under very good seeing
conditions.
Results: High magnetic flux density regions are
not necessarily associated with G-band bright points. We refer to the
observed extended areas with high magnetic flux density as magnetic
islands to separate them from magnetic elements. We discover that G-band
bright points tend to be located near the boundary of such magnetic
islands. The concentration of G-band bright points decreases with inward
distance from the boundary of the magnetic islands. Moreover, G-band
bright points are preferentially located where magnetic flux density is
higher, given the same distance from the boundary. There are some bright
points located far inside the magnetic islands. Such bright points have
higher minimum magnetic flux density at the larger inward distance from
the boundary. Convective velocity is apparently reduced for such high
magnetic flux density regions regardless of whether they are populated
by G-band bright points or not. The magnetic islands are surrounded by
downflows.
Conclusions: These results suggest that high magnetic
flux density, as well as efficient heat transport from the sides or
beneath, are required to make magnetic elements bright in G-band.
Title: On the Moat-Penumbra Relation
Authors: Vargas Domínguez, S.; Bonet, J. A.; Martínez Pillet, V.;
Katsukawa, Y.; Kitakoshi, Y.; Rouppe van der Voort, L.
Bibcode: 2007ApJ...660L.165V
Altcode: 2007astro.ph..2713V
Proper motions in a sunspot group with a δ-configuration and close to
the solar disk center have been studied by employing local correlation
tracking techniques. The analysis is based on a more than 1 hr time
series of G-band images. Radial outflows with a mean speed of 0.67
km s-1 have been detected around the spots, the well-known
sunspots moats. However, these outflows are not found in those umbral
core sides without penumbra. Moreover, moat flows are only found
in those sides of penumbrae located in the direction marked by the
penumbral filaments. Penumbral sides perpendicular to them show no
moat flow. These results strongly suggest a relation between the
moat flow and the well-known, filament-aligned Evershed flow. The
standard picture of a moat flow originating from a blocking of the
upward propagation of heat is discussed in some detail.
Title: Evidence of an association between the presence of penumbrae
and strong radial outflows in sunspots
Authors: Vargas Domínguez, S.; Bonet, J. A.; Martinez Pillet, V.;
Katsukawa, Y.
Bibcode: 2006astro.ph.11500V
Altcode:
Time series of high-resolution images of the complex active region NOAA
10786 are studied. The observations were performed in G-band (430.5 nm)
and in the nearby continuum (463.3 nm), on July 9, 2005 at the Swedish
1-meter Solar Telecope (SST) in La Palma. Granular proper motions in the
surroundings of the sunspots have been quantified. A large-scale radial
outflow in the velocity range 0.3 - 1 km s^[-1] has been measured around
the sunspots by using local correlation tracking techniques. However,
this outflow is not found in those regions around the sunspots with
no penumbral structure. This result evidences an association between
penumbrae and the existence of strong horizontal outflows (the moat)
in sunspots.